Please Note: This article is written for users of the following Microsoft Excel versions: 2007, 2010, 2013, and 2016. If you are using an earlier version (Excel 2003 or earlier), this tip may not work for you. For a version of this tip written specifically for earlier versions of Excel, click here: Understanding Functions in Macros.

Understanding Functions in Macros

by Allen Wyatt
(last updated December 5, 2015)

4

You already know that you can use subroutines in your macros. VBA also allows you to define functions that can be used in your macros. The difference between functions and subroutines is that functions can return values, whereas subroutines cannot. Consider the following macro:

Sub Macro1()
    TooMany = TestFunc
    If TooMany Then MsgBox "Too many columns selected"
End Sub
Function TestFunc()
    TestFunc = False
    If Selection.Columns.Count > 10 Then
       TestFunc = True
    End If
End Function

The macro (Macro1) calls the TestFunc function. This function returns either the value False or True, depending on a test it performs. Macro1 then acts upon the value returned. Notice that the function name can appear on the right side of an equal sign. This makes functions very powerful and an important part of any program. Within the function the result is assigned to TestFunc, which is the name of the function itself; this is the value returned by the function.

As with subroutines, you can also pass parameters to your functions. This is illustrated in the following macro:

Sub Macro1()
    A = 12.3456
    MsgBox A & vbCrLf & RoundIt(A)
End Sub
Function RoundIt(X) As Integer
    RoundIt = Int(X + 0.5)
End Function

This simple macro (Macro1) defines a number, and then uses a message box to display it and the result of passing the number to the RoundIt function. The output is 12.3456 and 12. Notice that the parameter should be passed to the function within parentheses. Also notice that the function does not use the same variable name as it was passed. This is because VBA reassigns the value of X (what the function needs) so it matches the value of A (what the program is passing to the function). The important thing to remember in passing parameters to functions is that your program must pass the same number of parameters as the function expects and the parameters must be of matching types and in the proper order.

Note:

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ExcelTips is your source for cost-effective Microsoft Excel training. This tip (11765) applies to Microsoft Excel 2007, 2010, 2013, and 2016. You can find a version of this tip for the older menu interface of Excel here: Understanding Functions in Macros.

Author Bio

Allen Wyatt

With more than 50 non-fiction books and numerous magazine articles to his credit, Allen Wyatt is an internationally recognized author. He  is president of Sharon Parq Associates, a computer and publishing services company. ...

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Comments

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What is 6 - 3?

2015-12-08 10:21:47

R Grealish

I think the point of my comment has been misunderstood (My fault in not expressing my self well).

I was not commenting on the specific tip whose purpose I fully understand. I took the code in the function as an example of a more general point I was trying to make which was why use more code than you need to. I will construct an example without using the code in the tip.

Consider the following VBA code fragment (which is not necessarily part of any function or subroutine)

result = false
if a > b then
result = true
end-if

In my view this code fragment could be written more succinctly as

result = a > b


2015-12-07 13:00:27

R Lowe

R Grealish, in fact a function call isn't necessary. The function call could have been replaced with:

If Selection.Columns.Count > 10
Then MsgBox "Too many columns selected"
End If

The point of this tip is just to demonstrate the difference between subroutines and functions.


2015-12-07 12:55:53

CJ

The example for TextFunc should work, but best programming practices suggest that the TextFunc function be defined as returning a Boolean data type.


2015-12-05 07:19:59

R Grealish

In many code examples, code of the following structure appears

TestFunc = False
If Selection.Columns.Count > 10 Then
TestFunc = True
End If

(taken from the tip).

It is unclear to me why the simpler and equivalent code is not used

TestFunc = Selection.Columns.Count > 10


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