User Defined Function in VBA

Updated on June 5, 2024
Article byJeevan A Y
Edited byAshish Kumar Srivastav
Reviewed byDheeraj Vaidya, CFA, FRM

Excel VBA User Defined Function (UDF)

Microsoft offers us many built-in functions to speed up the work in Excel. However, we can create our functions using VBA coding, which is technically called “User-Defined Functions” (UDF). They are also called “custom functions” in Excel VBA.

Any formula we can access from the worksheet with a piece of code is called UDF. In simple terms, any formula not built-in but available in Excel is called “User Defined Functions.”


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How to Create User-Defined Functions?

Even though UDF is part of our module, they are not part of our regular Subroutine in VBA. It is called a Function procedure in VBA. Like how we start the macro coding with the word SUB similarly, we need to start this by using the word “Function.” Sub procedure has a start and End. Similarly, the Function procedure has “Start” and “End.”

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You can download this VBA User Defined Function Excel Template here – VBA User Defined Function Excel Template

Example #1 – Create a Simple UDF Sum Function

We will create our SUM function in excel by adding up two numbers.

  • To start the coding, start the word “Function” in one of the modules.
VBA Function Return Example 1
  • Like how we name the macro similarly, we need to give a name to our Function. We have used the name as a formula name.
VBA Function Return Example 1-1

Unlike subroutine, we cannot simply press the “Enter” key to create a procedure. But, we need to mention arguments here.

For example, look at the below syntax of the worksheet function SUM.

SUM Formula.

Number 1 and Number 2 are arguments of the function SUM.

  • Similarly, we need to mention our arguments.
User Defined Function in Excel VBA Example 1-2

Here, we have declared the arguments “x as Integer” and “y as Integer.” Since we add numerical value, we only need to assign the data type as a numerical data type.

After declaring the arguments, we have assigned the return type of the integer too because the result given by the Function “OurSum” is also a numerical value.

  • Now, inside the function, we need to mention the formula we will use. Here, we need to use the function to start with.
User Defined Function in Excel VBA Example 1-3

We mentioned the formula name “OurSum” should add x and y.

  • Save the code and go to the worksheet.
VBA Function Return Example 1-4
  • We have entered a few numbers here. Open the equal sign and start typing “OurSum.” We can see the formula name appearing here.
VBA Function Return Example 1-5
  • Like how we select cells, similarly, select two cells separately.
User Defined Function in Excel VBA Example 1-6
  • After selecting two cells, press the “Enter” key for results.
VBA Function Return Example 1-7

So, it works the same as our regular SUM function.

  • Now, we will change the numbers.
User Defined Function in Excel VBA Example 1-8
  • Now again, we will apply the function we have created.
VBA Function Return Example 1-9

We got error values except for the first cell.

You must be thinking about why we got an error.

If you observe cells A2 and B2, we have values of 48,170 and 21,732. Since we have assigned the data type as “Integer,” it cannot hold any number more than 32,767. It is the reason we got the Excel error as #NUM!.

Now, we will add numbers that are less than 32,767.

VBA Function Return Example 1-10

In the above image, all the numbers are integers, i.e., less than 32,767.

In the first cell, we got the results. But in the second C2 cell, we got the error value as #VALUE!.

Even though both the numbers are less than 32,767, we still got the error.

It happened because we have declared the result also as “Integer.”

User Defined Function in Excel VBA Example 1-11

So, when we add 16,000 and 17,229, we will get a value like 33229, which is more than the integer data type limit of 32,767. So, the “End” result is an error value.

Example #2 – Create a Function to Test Logical Values

We will create one more function to test the logical values. We need a function that returns “Good” if the number is >=60, and we need the result as “Bad” if the number is <=50.

Step 1: Start the Function procedure and give a name to the procedure.

User Defined Function in Excel VBA Step 1

Step 2: Give the argument as “TestScore as Integer.”

VBA Function Step 2

Step 3: Our “End” result should be either “Good” or “Bad,” so the result should be in the string.

VBA Function Step 3

Step 4: First, we need to test whether the score is >=60. Use IF condition to test.

VBA Function Step 4

Step 5: If the test score is >=60, we need the function to return the result as “Good.” So TestResult = “Good.”

If Condition

Step 6: If the test score is less than 60, the function result should be “Bad.”

Else Condition

We have finished everything now.

  • Save the code and go to the worksheet.
Example 2 (Excel Data)

We have entered a few numbers here as a test score.

  • Apply the function we have created to arrive at results.
Check TestResult
  • Select the cell and press the “Enter” key.
Logical Test Result

This is what UDF is all about.

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This article is a guide to User Defined Function in VBA. Here, we learn how to create a user-defined function (UDF) in VBA along with examples and a downloadable Excel template. Below are some useful Excel articles related to VBA: –