Creating User-Defined Functions (UDFs) in Excel

User-Defined Functions (UDFs) in Excel allow you to create custom formulas to perform specialized calculations that are not available through built-in functions. By creating UDFs, you can extend the functionality of Excel to suit your specific needs.

How to write your own functions?

Creating custom functions is similar as writing VBA code for buttons. Open the VBA Editor and create new module. And now you can write your UDF code.

To write VBA code for custom function, you have to use the “Function” statement. Here is how to do it step by step:

Use the “Function” statement followed by the name of your function.
Specify the arguments within parentheses, along with their data types.
Write the code that performs the desired calculations.
Assign the result to the function name using the equal sign.
Use the “As” keyword to define the data type of the function’s return value.

Here's a simple UDF that calculates the square of a number:

Function SquareNumber(ByVal number As Double) As Double

SquareNumber = number * number

End Function

Close the VBA Editor to return to the Excel workbook. You can now use your custom UDF just like any other built-in function in Excel.

When creating UDFs, make sure to follow VBA programming rules and handle any potential errors.

Custom UDFs are available only in the workbook where they are defined. To use them in other workbooks, you'll need to copy the code or create an add-in.

UDFs provide flexibility and customization to meet your unique requirements and automate complex calculations.