User Defined Function in Excel VBA | Step by Step Guide to Creating UDF

User-Defined Function (UDF) in Excel VBA?

Microsoft serves us with many built-in functions to speed up the work in excel. This is so amazing to work with, however using Excel VBA coding we can create our own functions and those functions are technically called “User-Defined Functions” (UDF). “User-Defined Functions” or UDFs are called “custom functions” in excel VBA. Any formula which can be accessed from the worksheet with a piece of code is called as UDF.

In simple terms, any formula which is not built-in but available in Excel is called UDF in VBA.

How to Create User-Defined Functions in VBA?

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

Example #1 – Create a Simple UDF Excel Function

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

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

To start the coding start the word “Function” in one of the modules.

Like how we name the macro similarly we need to give a name to our Function as well. This name is used as a formula name.

Unlike subroutine, we cannot simply hit enter to create a procedure but we need to mention arguments here.

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

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

Similarly, we need to mention our arguments.

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

After declaring the arguments I have assigned the return type of the Integer too. Because result given by the Function “OurSum” is also a numerical value.

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Now inside the function, we need to mention the formula we are going to use. Here we need to use the function to start with.

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

Ok, save the code and go to the worksheet.

I have entered a few numbers here. Open equal sign and start typing OurSum. You can see the formula name appearing here.

Like how we select cells similarly select two cells separately.

After selecting two cells hit enter key to have results.

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

Ok, now I will change the numbers.

Now again I will apply the function we have created.

Oh!!! We got error values except for the first cell.

You must be thinking about why we go error.

If you observe the cell A2 and B2 we have values 48170 and 21732. Since we have assigned the data type as Integer it cannot hold any number more than 32767. This is the reason we got the excel error as #NUM!.

Now I will add to numbers that are less than 32767.

In the above image, all the numbers are integer numbers i.e. less than 32767.

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

Even though both the numbers are less than 32767 still we got the error.

This is because we have declared the end result also as Integer.

So when we add 16000 and 17229 we will get the value like 33229 which is more than the integer data type limit of 32767. So the end result is error value.

Example #2 – Create UDF Function to Test the 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.