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Power Formula Auditing The Power Tool for every Excel User Power Formula Auditing The Power Tool for every Excel User Language: english File: EPUB, 1.91 MB Your tags: 0 / 0

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Power Formula Auditing: The Power
Tool for every Excel User
HC Chan

Copyright © 2017 HC Chan
All rights reserved.
ISBN:

Preface
A journey of a thousand miles begins with a single step.
If you have to step your way through a thousand miles, will you do it? What if
you have a car or a plane for your journey of a thousand miles?
Excel has this very useful ability (called formula auditing) to trace precedents
and dependents, which draws arrows to connect cells. These arrows are very
useful for understanding how cells use values from other cells. Cell
connections have other powerful uses. For example, cell connections for an
entire spreadsheet can show us how the spreadsheet is structured. Often, cell
connection arrows can reveal potential errors.
Excel’s formula auditing is, however, very tedious to use as it is limited to
tracing one cell at a time, and one level at a time.
You have to go step by step.
This unique spreadsheet book shows how you can easily enhanced the tracing
ability of Excel, by downloading Power Formula Auditing (Excel 2013). It is
as if you can now zoom over a thousand miles, with a few clicks on the
spreadsheet.
This book goes beyond simple tracing of precedents and dependents. It shows
you how you can quickly and easily gain an overview of your spreadsheet
model, with just a few clicks of Power Formula Audit. The automatically
generated cell connections allows easy understanding and error detection, as
illustrated in the book.
The overview for a spreadsheet is like a map of the mountains and rivers and
with all the hiking trails. A normal spreadsheet is like a map without showing
any hiking trails. Which map do you want to use for hiking?
This book is meant for all types of Excel users. It is meant for both novice and
expert users. Whether you create spreadsheets or you work with other people’s

spreadsheets, this book will be very useful for you.
This book is especially useful for people who check other people’s
spreadsheets. If you are a spreadsheet teacher, a spreadsheet auditor ; or a
manager who gets spreadsheet reports, this book is a must read.
Even if you read only your own spreadsheets, this book gives you better and
more efficient methods to look through your own spreadsheets.
With Power Formula Auditing, you gain a new powerful perspective about
spreadsheet models.

Contents
1. Introduction to Influence Charts
Example 1: Interest Calculation
Example 2: A summation of expenses.
2. Uses of Influence Charts
3. An Under-utilized but Powerful Tool
4. Precedents and Dependents
Trace precedents
Trace dependents
A quick display of immediate precedents
Box arrow for a range of precedent cells
5. Wrong or Missing Connections: A Common Error
Example 1: A payroll model
Example 2: An economics model
6. An Enhanced Influence Chart: Power Formula Auditing
7. Tracing Precedents / Dependents for Multiple Cells
8. Examples of Overviews
Example 1: A simplified balance sheet
Example 2: A company’s consolidated balance sheet
Example 3: A company’s statement of income

Example 4: A Personal Budget Model
9. Special Cases for Trace Precedents and Trace Dependents
Offset formula in Excel
Vlookup & Hlookup formulas
Formulas that cross worksheets
10. A Special Chapter for Spreadsheet Teachers
11. Influence Charts help What-If Analysis
12. Conclusion
References
Appendix A. How to add Power Formula Auditing to Excel?
Appendix B. How to uninstall PowerFormulaAudit from Excel?
Appendix C. PowerFormulaAudit Menu

1. Introduction to Influence Charts

“More often than not just one person in a company has the
knowledge of how the financial spreadsheet models are
constructed. Other people are unable to understand and therefore
check the analysis. The potential for errors is massive.”
The Telegraph. 2015.

This book focuses on one main topic: the influence chart. An influence chart is
a very powerful tool. An influence chart provides an overview of your Excel
model. It shows all the items (the values and formulas) and how these are
connected to one another.
An influence chart is so important that experts recommend that we draw an
influence chart before we enter the values and formulas to develop an Excel
model.
As we all know, most people don’t do that. We simply enter the values and
formulas and design the model as we type.
Furthermore, the connections among items are not obvious in an Excel model.
In fact, the connections are very well hidden.
Even when we are handed an influence chart for an Excel model, we don’t
know whether the Excel model really follows the influence chart.
This book shows how we can easily and quickly draw an influence chart from
an Excel model, with the help of Power Formula Auditing. The automatically
generated influence chart shows how the Excel model is really organized.
An influence chart has many important uses. It provides an overview of the

Excel model. This enables us to understand the model at a high level, to know
how various components are connected.
A good influence chart will also give visual clues of the components in an
Excel model.
In addition, an influence chart is very useful for identifying errors. Some errors
are very obvious once the influence chart is drawn. These will be illustrated in
the later chapters.
Excel has some basic, and tedious, functions to draw an influence chart from
an Excel model. This book illustrates how to use these functions. In addition,
this book will illustrate a special-purpose add-in software that gives enhanced
influence charts, and with less effort.
Let us consider a few simple examples of influence charts.

Example 1: Interest Calculation
This is a very simple example for interest calculation. It calculates the interest
earned after one year, given the deposit amount and the interest rate.

Figure 1. Interest Calculation Influence Chart

Note that the influence chart shows the connections, but usually not the actual
values.
This next figure shows how the Excel model looks like. The model includes
the actual values, e.g., 2% for the interest rate. However, the connections are
not show visually. The connections are “hidden” within the formula for interest
earned.
Looking at the formula for cell D2 (=C4*C5/100), we know that cell D2 is
linked to cell C4 and C5. (A cell is a single rectangle in a spreadsheet table.)

Figure 2. Interest Calculation Excel Model

For a single formula and a few cells, finding the connections is not difficult.
But when there are many formulas and cells, finding the connections is very
tedious.
However, with Excel, we have the ability to generate a good influence chart
with only a few clicks. The next figure shows the result. Note that the
connections are now shown visually with arrows.

Figure 3. Excel generated Interest Calculation Influence Model

Example 2: A summation of expenses.
This model is about monthly expenses. The total expense is the sum of rent,
food, entertainment, clothing and transport expenses. The influence chart is
shown below.

Figure 4. Expenses Influence Chart

The Excel model is shown below.

Figure 5. Expenses Excel Model

The next figure shows the connections generated in Excel.

Figure 6. Excel generated Expenses Influence Model

Notice that Excel does not show the separate arrows that we have drawn in the
original influence chart. When the formula uses a range of cells (D2:D6), a box
over the range of cells is shown with a single arrow.

2. Uses of Influence Charts

If people draw an influence diagram before beginning to construct
their spreadsheet then they will build a better model
Australasian J. of Information Systems. 2011.

Influence charts are well recognized to be good for designing a spreadsheet
model. What is not so well recognized is that an automatically generated
influence chart is also very good for understanding a spreadsheet model, and
even for detecting errors.
In general, an influence chart is very good at showing the overall connections
in an Excel model. In addition to seeing an overview of the Excel model, users
can zoom in to look at details on any connection.
The Excel generated influence chart has another very important use. Potential
errors can be easily seen.
In a famous academic paper about GDP growth, a few rows of data were left
out of the average calculation. More information about this case can be found
here: The spreadsheet error in Reinhart and Rogoff’s famous paper on debt
sustainability.
(This
URL
is
http://blogs.marketwatch.com/thetell/2013/04/16/the-spreadsheet-error-inreinhart-and-rogoffs-famous-paper-on-debt-sustainability/)
The spreadsheet used in the academic paper is shown below. It is not easy to
tell if the averages in the last row are correct.

Figure 7. An Excel Model about GDP Growth

The next figure shows the model with the automatically generated influence
chart.
It is now quite easy to see that the last few rows of data were left out of the
average calculation. The blue boxes (used for sum and average functions
which state a range of cells) do not cover the last few row.
It is obvious that row 25 to row 29 are not included.

Figure 8. Trace Precedents highlights Errors in GDP Growth Model

When all the rows are correctly included in the average, the influence chart
should appear as in the next figure.
This example shows how an influence chart can give clear clues about
possible errors.
In the later chapters, we will enhance the influence chart with additional
software that can be added to Excel (add-ins software). The enhanced
influence charts are easier to use, have more features, and are better at
indicating potential errors.

Figure 9. Trace Precedents for Corrected GDP Growth Model

3. An Under-utilized but Powerful Tool
While an automatically generated influence chart is very powerful for users,
most users do not know about this.
According to a study about MBA users (Baker, K. R., Foster-Johnson, L.,
Lawson, B., & Powell, S. G. (2006). A survey of MBA spreadsheet users.
Retrieved April, 30, 2010.), users do not make much use of technology in
checking their spreadsheets.
Only 24% make use of “formula auditing” toolbar that is used for generating
influence charts.
There are many new and easy to use add-in software programs that can help
users check their spreadsheet. Some are included in Excel (formula auditing),
and others may cost a few thousand dollars.
This book will explain how to use the formula auditing functions that are
originally in Excel.
It will show users how to get the advance software (Power Formula Auditing)
to easily generate informative influence charts, and illustrate the results from
this software, compared with the results from the basic auditing functions
provided in Excel.

4. Precedents and Dependents
These functions are essential for any spreadsheet user. If you want to
understand how your spreadsheet formulas are connecting all the cells, tracing
precedents and dependents is the best method in Excel.
A formula in a cell (X) may refer to another cell (Y). Then, Y is called the
precedent of X, and X is called the dependent of Y.
Excel provides an easy way to identify all precedents of a cell, or all
dependents of a cell.
Simply select a cell, and click the "Trace Precedents" or "Trace Dependents"
button. These buttons are organized under the “FORMULAS” menu in Excel.
The set of formula tracing buttons is called “formula auditing”, or “auditing
toolbar”.

Figure 10. Precedents / Dependents Tracing Buttons

Trace precedents
A simple Excel model is shown in the next figure.

Figure 11. A Simple Excel Model

Excel will draw the precedent arrows after a few clicks. Select (click on) cell
D10. Then click “trace precedents” a few times. Each click traces the
precedents one level further.

Figure 12. A Simple Excel Model with Precedents Traced

Note that the beginning of an arrow has a big dot. This is important to bear in
mind when we look at many overlapping arrows. The end of an arrow has an
arrow-head. An arrow goes from a precedent cell to a dependent cell.
Tracing precedents is particularly useful when we want to know what other
cells (values and formulas) affect the selected cell. For example, if cell D6 is
the profit of a company, the precedents show the other items that have an effect
on the profit value.
Looking at arrow connections is much easier than looking at formulas in each
cell, which can also be done by showing all formulas at once (“Show
Formulas” button).

Figure 13. A Simple Excel Model with Formulas Shown

Trace dependents
The “Trace Dependents” button produces similar results. For example, in the
next figure, we select cell A4. Clicking “Trace Dependents” will find the cells
dependent on A4, i.e., the cells with formulas that refer to A4.
The first click will show the immediate dependents (in this case, only one
arrow from A4 to C3). The second click will show the dependents of the
immediate dependents (in this case, another arrow from C3 to D6).
The “Trace Dependents” button is particularly useful when we want to know
how the Excel model will be affected when we change the values in a cell.
Tracing dependents show us all the cells that will be affected.

Figure 14. An Example for Tracing Dependents

A quick display of immediate precedents
If we are interested in only the immediate precedents of a cell (i.e., we don’t
want to trace the precedents of the precedents), there is a super quick method
to visually show them.
Simply double-click on a cell, its immediate precedents will be highlighted
with colors that match their cell reference in the formula.
An example is given below. By double-clicking on cell C7, the precedents are
shown. Cell A4 is shaded blue to match the blue color of “A4” in the formula.
Similarly, cell B4 is shaded red to match the red color of “B4” in the formula.
Unfortunately, there is no equivalent method to highlight dependents.
This technique is very fast and simple for tracing precedents of a single cell.
For some complex tracing, we need to go back to the “Trace Precedents” and
“Trace Dependents” buttons.

Figure 15. Formula Highlighting

Box arrow for a range of precedent cells
Where cells are stated one by one in a formula, the arrows are shown
separately. As we have seen earlier, where a formula states a range of cells,
e.g., A1:A5, the arrows are organized into one arrow. An illustration is shown
below.

Figure 16. Precedent Arrows for Individually Specified Cells

The above figure shows a formula where every precedent cell is explicitly
stated. Tracing precedent shows an arrow from each precedent cell.

Figure 17. Precedent Arrow for a Range of Cells

In the above figure, the formula indicates a range of cells. Trace precedent
shows the range of cells in a rectangle, and shows only one arrow from the
range of cells.
This box arrow will appear, e.g., in these formulas: =sum(A1:A10),
=average(A1:10), =count(A1:B10).
The box arrow can cover many rows and columns, as shown in the following
figure.

Figure 18. Precedent Arrow for a Multi-column Range of Cells

More examples of “Trace Precedents” pattern of arrows will be given later.
For example, what happens when a formula refers to a cell in another Excel
worksheet? What happens in complex formulas that look up a table of data,
such as vlookup?
If we trace the dependents of Ben’s English mark, the following figure will
appear. First select Ben’s English mark (click on it), then click on “Trace
Dependents”.

Figure 19. Trace Dependents

Since Ben’s English mark is used by only one cell, there is only one arrow
from there.
The “box arrow” drawn by “Trace Precedents” will not appear when we trace
dependents. It is a good point to bear in mind. Tracing precedents over an
entire worksheet may not give an identical set of arrows, compared to tracing
dependents.
The next figure shows the result when we trace the dependents for every cell
(click on “Trace Dependents” after selecting each cell). Notice that the pattern
of arrows is quite different.

Figure 20. Dependent Arrows do not have the box outline

5. Wrong or Missing Connections: A Common Error
A wrong connection happens when a formula in a cell refers to a wrong cell.
This is a very common error. But it is notoriously difficult to find just by
looking at formulas one by one. With the precedent/dependent arrows, the error
may become visually obvious.
One wrong connection can have big consequences. Here are a few cases.
$15M mistake in county books being corrected: Treasurer says spreadsheet
error had no financial impact [Herald-Times, Bloomington, Ind.]
(URL: http://www.tmcnet.com/usubmit/2009/11/21/4494996.htm)
"The financial discrepancy came to light earlier this month during a county
council work session. At that time, Smith described it as a reporting error that
happened when two employees switched jobs, after which the new employee
in her office began using a different spreadsheet that contained a broken data
link. A single entry error compounded over the past few months to make the
apparent discrepancy larger, she said at the time, eventually leaving the
county's books showing $15 million more than the bank said it had."
Trustee's Office mistake to cost taxpayers $12,500
(URL:
http://archive.knoxnews.com/news/local/trustees-office-mistake-tocost-taxpayers-12500-ep-402350878-357355791.html)
"He said the reports his office sent to KPMG didn't include one account, which
threw off his department's financial statements. The total cash on hand for June
30 that the office should have reported was $128.9 million, he said, and not
$122.7 million, which was what was sent to the auditor. It occurred when one
account wasn't correctly linked into an Excel spreadsheet."

Example 1: A payroll model
For an example of how precedent arrows can give clues to errors, consider
this spreadsheet (given in this article (Ferret Out Spreadsheet Errors, Use
Excel’s tools to uncover and correct formula problems.by Mark G. Simkin,
January 31, 2004, JournalofAccountary.com)
The precedent picture generated from the spreadsheet is given below. This is
generated by selecting the “total” cell (G14) and clicking “Trace Precedents” a
few times.
Irregularities in the blue dots indicate potential errors. A blue dot on a cell
means that the cell is the beginning of one or more precedent arrows.
Lack of a blue dot means that the cell is not used (for the set of precedent
arrows shown). A missing blue dot may indicate a missing connection.
Can you spot all the irregularities?

Figure 21. A Model with Missing Connections

Notice that in column C (regular hours), only one cell has a blue dot, indicating
that this cell is used in some formula in other cell or cells. More importantly,

the other cells in column C are not used, as they do not contain any blue dots.
This pattern strongly suggests the presence of errors, and these cells should be
checked thoroughly.
The relevant portion is shown below.

Figure 22. Missing Dots, Missing Connections

In column D (overtime hours), there is also a cell without a blue dot, different
from its neighbors. This also indicates a potential error. If you look harder, you
can find that cell F7 also has a different arrow pattern compared to its
neighbors.
This example illustrates a very important use of the automatically generated
influence chart. While the items are there, the connections are missing.
The influence chart makes the missing connections visually obvious.

Example 2: An economics model
This economics model, shown earlier, is repeated below, to illustrate another
arrow pattern that indicates potential errors. This is about the position of box
arrows. The boxes miss out the intended rows (rows from 25 to 29).

Figure 23. Excluded Rows in Faulty Range Cell Formulas

6. An Enhanced Influence Chart: Power Formula Auditing
Excel’s tools for tracing precedents and dependents are very useful. They can
be make even more useful with some additional programming. An enhanced
tool for generating better influence charts can be downloaded here: Power
Formula Auditing (Excel 2013).
Power Formula Auditing has very good improvements over Excel’s tracing of
precedents and dependents. The main improved features include:
The ability to select many cells for tracing precedents and
dependents. Excel’s trace precedents/dependents buttons are limited to
only one selected cell.
- The ability to get an entire overview with just 2 clicks. Simply select
the entire spreadsheet, and click one button on the new toolbar.
Currently, to get an overview may require a few hundred clicks, and
most people will just not do it, and they will miss out on powerful
influence charts.

Power Formula Auditing is developed based on the original formula auditing
functions. It is unlikely to change the appearance of spreadsheets. However, it
is advisable to work on duplicate copies.
Power Formula Auditing may be slow for very big models, e.g., a thousand
cells. The functions may take some time to complete their jobs. Excel’s “Trace
Precedents” avoids the time delay by limiting to only one selected cell.
This software works for Windows Excel 2013 and 2010. It may not work for
older versions of Excel. It is the product of spreadsheet research by the author
and others at the National University of Singapore. (The URL to download is:
https://drive.google.com/open?id=0B926LJ4H-JLIdHItcWE3WEJnNms)
The software can be easily added to Excel 2013, as an add-in software. This is
explained in Appendix A. Appendix B explains how it can be removed.

7. Tracing Precedents / Dependents for Multiple Cells
Precedents for a single cell
Excel’s “Trace Precedents” and “Trace Dependents” works only for one cell.

Figure 24. Trace Precedents work for one cell.

For example, in the above figure, 3 cells are selected (as indicated by the
green border around B7:D7). “Trace Precedents” show the arrows only for
one cell (B7).
Multi-Precedents for a block of cells
With Power Formula Auditing, we can select one or many cells for tracing
precedents. The function/button is called Multi-Precedents

Figure 25. Power Formula Audit Buttons

It is a powerful extension of the “Trace Precedents” button in Excel.
Using the same expense example, we can select B7:D7. One click of MultiPrecedents will draw precedents arrows for all the selected cells, as shown in
the next figure.
"Multi-Precedents" works on 1 cell, a block of cells, and even an entire
worksheet. It helps to identify the important cells and their connections.

Figure 26. Multi-Precedents work for many selected cells

Multi-Precedents for an entire worksheet

In addition to selecting a block of cells, we can also select the entire
worksheet.
Selection of an entire worksheet can be done by clicking on the square on the
top left corner, above row 1 and to the left of column A, as shown in the
following figure.

Figure 27. Selection of an entire Worksheet

Multi-Precedents can then be applied to the selection.
As for “Trace Precedents”, each click of “Multi-Precedent” will show another
level of Precedents.
Remove Multi-Precedents
The button to remove multi-precedent is labeled “Less-MultiPre” . Each click
removes one level of the precedent arrows.
Multi-Dependents
The “Multi-Dependents” and “Less-MultiDep” buttons work in a similar way
to the “Multi-Precedents” and “Less-MultiPre”.

As example is shown below. We first select 3 cells, B2:D2, then we click on
“Multi-Dependents.” The result is the drawing of 3 arrows from the selected
cells. With Excel’s “Trace Dependents”, we have to select B7, click “Trace
Dependents”, and repeat for C7, and D7.

Figure 28. Multi-Dependents Example

8. Examples of Overviews
Often, when we are faced with a spreadsheet, we have no idea how the
spreadsheet is organized and where we can start. The following examples
illustrated how an overview can be easily generated.
An overview allows us to have a high level view, and identify where to zoom
in for closer looks.

Example 1: A simplified balance sheet
The next figure shows a much simplified balance sheet. , which shows a
standard format for a company’s balance sheet. This is how it normally looks
without an influence chart.

Figure 29. A Balance Sheet

The next figure shows the same balance sheet with an influence chart drawn
over. The figure is obtained in two clicks. One click selects the entire sheet.

The second click is on “MultiPrecedent” button.
The overview shows 4 components. Each component is a “group” of cells
connected by arrows, and there are no arrows across groups.

Figure 30. A Balance Sheet with Components Highlighted

Example 2: A company’s consolidated balance sheet
This example uses a consolidated balance sheet provided by a big corporation.
The next figure shows how it looks like normally, without the influence chart.
The subsequent figure, with the influence chart showing the components and
precedent arrows, is produced in 2 steps:
·

Select the entire worksheet

·

Click the “Multi-Precedent” button

The overview created by the blue precedent arrows shows 8 separate
components, with two for each quarter. Each quarter has one component for
assets and one component for liabilities.

Figure 31. A Company consolidated balance sheet

Figure 32. Quarterly Balance Sheet with Precedent Overview

Example 3: A company’s statement of income
This example is from the same corporation. It shows how a worksheet with
one component can show separated components when only part of the
worksheet is selected for analysis.
The next few diagrams show the following:
·

The worksheet as it appears normally.

·

The entire worksheet with precedents shown (by clicking “MultiPrecedent” button”

·

The partial worksheet with only quarterly columns selected, and with a
click on “Multi-Precedent” button”. It is quite clear that the quarterly
data are connected through the annual total in the rightmost column. But
without the rightmost column, the quarterly columns are separated
components. A partial selection can also present a less cluttered view.

Figure 33. Income Statement

Figure 34. An Overview of the Income Statement

Figure 35. A Quarterly Analysis of the Income Statement

Sometimes, it is better to analyze only part of the worksheet. As in this case,
the arrows and color boxes for each quarter are not messed up by another set
of horizontal arrows for the annual totals.
In general, it is good to try overviews or partial overviews, to allow us to

view the Excel model with different perspectives.

Example 4: A Personal Budget Model
This example of a personal budget spreadsheet is from vertex42.com/

Figure 36. A Personal Budget Model

With the Multi-Precedent button, we can get the following figure with
precedent arrows with 2 clicks (select the entire worksheet and click on the
Multi-Precedent button).
This picture shows us the overall structure of the model. For example, there

are many tabular structures and all arrows eventually point to the upper right
corner.
We see that sub-totals within each table are used in the total calculation, at the
top right corner. We also see that budget-actual differences in each table are
not used for the total difference.

Figure 37. Precedents for Personal Budget Model

9. Special Cases for Trace Precedents and Trace
Dependents
For some types of formula, trace precedents and trace dependents may give
results that are not so natural, intuitive or even misleading. Some examples are
discussed in this chapter.
Power Formula Auditing, which builds upon the original trace precedents and
trace dependents, have the same limitations.

Offset formula in Excel
One example is the Offset formula. A explanation for this formula is at
Microsoft support (How to use the Offset formula in Excel).
The offset formula can be used to calculate, say, weekly data when we have
daily data. The formula will, e.g., sum the first 7 days, and each subsequent 7
days.
In the next figure, the top rows are the daily usage of 3 items (milk, sugar and
butter). For clarity, only the milk entries have data.
To get the weekly summation for week 1, we enter this formula into cell B8
=SUM(OFFSET($B3,0,(B$8-1)*7,1,7)).
This formula can be copied and pasted for subsequent weekly summations. For
example, after copy and paste, cell C8 will have this formula:
=SUM(OFFSET($B3,0,(C$8-1)*7,1,7))
Without the offset formula, we have to design and type a different formula for
each weekly summation. So the offset formula saves a lot of mental calculation
and typing.
The effortful method is illustrated in the bottom half of the figure. Cell B17
contains =SUM(B12:H12), and cell C17 contains =SUM(I12:O12). Note that
we cannot just copy the formula from B17 and paste to C17. With this method,
the precedent arrows show very clearly the daily cells that are being summed
into the weekly cells (the precedent arrows in the bottom half of the figure).
In contrast, the precedent arrows for the offset formula do not give much
information. They show only the cells that are explicitly mentioned in the offset
formula, but not the ultimate cells that are used in the summation.
Tracing precedents become much harder with the offset formula. Cells that are
used by the offset formula but not explicitly included in the formula will show
up as stand-alone cells, as shown in the next figure.
The result could be visually misleading, unless we are aware of it.

Figure 38. Precedents for Offset Formula

Vlookup & Hlookup formulas
The Vlookup function allows us to search a table based on a value in the first
column, and return a value from some other column along the same row as the
search value. An illustration is given at Microsoft support (VLOOKUP function).
The Hlookup function is a similar function which search based on the first row,
instead of the first column.
The next figure shows the trace-precedents arrows for vlookup and hlookup
formulas.
The arrows indicate the table used in the search, but does not pinpoint the cell
value that is returned. For example, the vlookup formula returns the birthdate in
cell B3.
Trace-precedent does not go into the results for formula evaluations.

Figure 39. Precedents for Vlookup /Hlookup Formula

Formulas that cross worksheets
In some complex situations, people organize their Excel model across a few
worksheets. It is possible to trace precedents across worksheets. However, it
is very difficult.
Consider a very simple example where one worksheet is used for a company’s
profit model for one year. Over a few years, there will be a few worksheets,
one for each year. In addition, there is a total worksheet that sums number
across the yearly worksheets.
Consider this very much simplified model where the purpose is solely to see
what happens when precedents are traced across worksheets. There are three
worksheets: All-years, 2016 and 2017, as shown in the following figure.
Notice the cross-worksheet formula (=‘2016’!C5+’2017’!C5).

Figure 40. Multi-Worksheet Model

What happen when we trace precedents from the All-years worksheet? We
select cell C5, then we click on “Trace Precedents”. The result is shown in the
next figure.

Figure 41. Cross-worksheet Precedent

Notice that the precedent arrow is a dash arrow and the beginning of the arrow
shows a table, indicating a worksheet. We can identify the precedent by
carefully double-clicking on the arrow. This will bring up a panel that shows
the precedent cells, as shown in the next figure.

Figure 42. Precedent Cells across Worksheets

Double-clicking on a cell reference in the panel will bring us to that cell (in its
own worksheet).
Tracing across worksheets is usually very difficult.

10. A Special Chapter for Spreadsheet Teachers
As teachers, when we ask students to develop spreadsheet solutions, how do
we check the correctness of the answers?
Checking other people’s spreadsheet model is well recognized as a difficult
and tedious task.
One way used by teachers to reduce the difficulty is to have a spreadsheet
template where students must fill in formulas and values at specially
designated cells.
The student answers are then compared with the correct solution, e.g., we can
overlay worksheets and check the corresponding values.
Even then, a common problem is that students may simply enter the expected
value instead of the correct formula. For example, a value of 10 may be
entered instead of a formula, say, =A1*B2. The current recommended check is
to turn formulas on and off, and visually check for values where formulas
should be. (The fast way to toggle formulas on and off is ctrl+`)
Power Formula Auditing is very suitable for doing this type of check: a value
when a formula should be. The precedent arrows drawn by “Multi-Precedents”
will show clues. There will be missing arrows, and /or the chain of arrows
will be disconnected.
The next figure shows a table to calculate yearly balance with different interest
rates for each year.

Figure 43. Yearly Interest Calculation

Suppose that instead of using the proper formula, a value of 10 is entered for
the interest earned in the first year. In the next figure, the top half shows the
table properly constructed while the bottom half shows the wrongly done table.
The missing arrow on the first row is quite obvious. (This figure is drawn by
selecting the table and clicking on “Multi-Precedents)

Figure 44. Precedent Patterns for Value versus Formula

More advance templates include specially hidden formulas or macros (small
programs in Excel VBA) that auto-check the answers.
An example of hidden checking formulas is from here: Quick Correct: A
method to automatically evaluate student work in MS Excel spreadsheets.
An example of macro checks is from here: Tale of Two Cities (and two
hurricanes): New Orleans. The spreadsheet provided to students has built-in
macros that check for correctness. In the following picture, "click to check
work" activates a macro to check the student work. Developing the macro is
not easy. It requires the teacher to know programming with VBA for Excel. Not
many spreadsheet teachers know VBA so well.
However, asking students to fill in Excel templates is like asking students to
fill in the blanks in an essay. It does not allow for creativity.
What if we allow students to design their spreadsheet answers without the

strict constraint and guidance of a template? That will require much effort from
the teacher to check through each differently designed solution.
That's where Power Formula Auditing comes in. Power Formula Auditing
allows us to easily have an overview of the spreadsheet as well as look into
connection details. This is done with a few button clicks and do not require
any VBA knowledge. Power Formula Auditing can be very helpful for
spreadsheet teachers.

11. Influence Charts help What-If Analysis
An influence chart is very useful if we want to do what-if analyses.
In general, a what-if analysis is when we change the value of a certain cell and
see what happens to another cell. Suppose we have a profit model, and we
want to see how a price change will increase our profit. For example, if price
is set at $11, what will be the profit?
Alternatively, using goal-seeking, which is also under the what-if analysis
menu, allows us to specify a value for a goal cell, and check what value is
needed for a precedent cell. For example, if we want the profit to be $1
million, what should be the price?
In a complex model, it may not be clear what cells can be changed or set with
goals for a what-if analysis. The influence chart plays an important role as it
will show us the input cells where we can change, or the output cells where
we can set a goal.
More information about what-if analysis can be found at Microsoft support
(Introduction to What-If Analysis). (URL: https://support.office.com/enus/article/Introduction-to-What-If-Analysis-22bffa5f-e891-4acc-bf7ae4645c446fb4)
Excel has another function similar to what-if analysis. This is the “Watch
Window” button under Formulas/Formula Auditing. “Watch Window” allows
us to select various cells to “watch” while we are editing the spreadsheet. The
watch window display the cell location, formula and value.
An influence chart will be very useful. It will help us to trace and watch the
dependent cells.

12. Conclusion
Influence charts are very important for looking at Excel models. Influence
charts, in providing an overview, helps us to understand Excel models.
It is easy and quick to automatically generate an influence charts from an Excel
model. Since the influence chart is generated from the model, errors in the
model will be reflected in the influence chart.
By looking at unusual or unexpected patterns in the influence charts, we can
find potential errors in the Excel models.
A word of caution is needed though. An influence chart can provide many
helpful ways to understand and check spreadsheet models. However, expert
domain knowledge is still needed for a thorough understanding of complex
spreadsheet models. Engineering knowledge is needed to understand
engineering spreadsheet models, and financial knowledge is needed to
understand financial spreadsheet models.

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Appendix A. How to add Power Formula Auditing to
Excel?
There are many “add-ins” software or applications. Excel has very detailed
guides on how to add in an “add-ins” application. Power Formula Auditing is
an “add-ins” application.
The steps are as follow:
·

Download the Power Formula Auditing add-in software
(PowerFormulaAudit_1.0.xlam) into any directory in your computer.

·

Add the software with the following steps:
o Click the File tab, click Options, and then click the Add-Ins category.
o In the Manage box, click Excel Add-ins, and then click Go.
o The Add-Ins dialog box appears.
o Browse to the directory where you save. PowerFormulaAudit_1.0.xlam.
Select the file.
o PowerFormulaAudit will show up in Add-Ins available box.

·

You may need to activate the add-in with the following steps:
o Click the File tab, click Options, and then click the Add-Ins category.
o In the Manage box, click Excel Add-ins, and then click Go.
o The Add-Ins dialog box appears.
o In the Add-Ins available box, select the check box next to the add-in that you
want to activate, and then click OK.

·

Close Excel. Do not delete the file for PowerFormulaAudit.

·

You can use Excel as per normal. The commands from Power Formula
Audit are in the menu for you to use with any Excel file.

The first time a Power Formula Audit button is used in a file, Excel may
prompt you to enable the macros.

The addition steps are further illustrated with the following screenshots:

Figure 45. File / Options /Add-ins Screenshot

Figure 46. After clicking "Go" from the previous screenshot

For more general and detailed information about add-ins and steps to add or
remove add-ins to your spreadsheet, please see this link from Microsoft

support (Add or remove add-ins).

Appendix B. How to uninstall PowerFormulaAudit from
Excel?
The add-ins will be there until you remove it. A simple way to remove
PowerFormulaAudit is to delete the PowerFormulaAudit file from the
directory. If the file is moved to another directory, Excel will not be able to
find the PowerFormulaAudit functions.

Another way is to deactivate the add-in, which will also remove the menu for
power formula audit. The steps are similar to the activation steps in Appendix
A.
The steps to deactivate are:
·

Click the File tab, click Options, and then click the Add-Ins category.

·

In the Manage box, click Excel Add-ins, and then click Go.

·

The Add-Ins dialog box appears.

·

In the Add-Ins available box, uncheck the check box next to the add-in that you
want to deactivate, and then click OK.

For more general and detailed information about add-ins and steps to add or
remove add-ins to your spreadsheet, please see this link from Microsoft
support (Add or remove add-ins).

Appendix C. PowerFormulaAudit Menu
The PowerFormulaAudit menu is shown below.

Figure 47.. PowerFormulaAudit Menu

PowerFormulaAudit has the following menu buttons, listed from left to right as
shown in the above figure.
Multi-Precedent
Excel’s “Trace Precedents” works only when one cell is selected, MultiPrecedent works on any number of selected cells, e.g., a single cell, a row /
column of cells, a block of cells, or even an entire worksheet. Where
applicable, every click shows the next level of precedents.
Since this function works on many selected cells at a time, the precedents may
not be strictly one level up. The reason is that the selected cells may already
have a few levels of precedents. In the case where an entire worksheet is
selected, this function will draw all the precedent arrows in the worksheet.
Multi-Dependent
This works in the same way as Excel’s “Trace Dependents”, but allow many
cells to be selected. Each click shows the next level of dependents.

As in the case of multi-precedents, the function does not go strictly by one
level of dependents. The reason is that the selected cells may already have a
few levels of dependents. When an entire worksheet is selected, this function
draws all the dependent arrows.
As illustrated earlier, dependent arrows may look different from precedent
arrows (particularly for box arrows).
Less-MultiPre
Every click reduces the arrows for the furthest level of precedents.
Less-MultiDep
Each click removes the arrows from the furthest level of dependents.
Erase Arrows.
This yellow “eraser” button removes all auditing arrows.
PowerFormulaAudit has a few limits.
·

For very big models, e.g., a thousand cells, the functions may take some
time to complete their job when the entire worksheet is selected. Excel’s
“Trace Precedents” avoids the time delay by limiting to only one
selected cell.

·

In rare cases, a formula may refer to an empty cell. For example, cell
A3 has this formula “=A1”, and cell A1 is empty (i.e., cell A1 has no
numeric value or string value, not even a space). Where an empty cell is
the precedent of another cell, the dependent arrow will not be drawn
with Multi-Dependent, e.g., when cell A1 is selected.. However, the
arrow will be drawn with Multi-Precedent, e.g., when cell A3 is
selected.

ABOUT THE AUTHOR
Dr. HC Chan has a PhD from the University of British Columbia. He has
teaching and research experience with spreadsheets. He taught a course on
decision modeling with spreadsheets, for a few years, at the National
University of Singapore. He also provided specialized training about
spreadsheet error detection to practitioners. His research about spreadsheet
users has been published at international journals and conferences.