How to Create a User Defined Function in Excel

Creating a User Defined Function (UDF) in Excel using Visual Basic for Applications (VBA) allows you to perform custom calculations beyond the capabilities of built-in Excel functions.

Step 1: Open the Visual Basic Editor

• Open Excel and press Alt + F11 to open the Visual Basic for Applications (VBA) editor.

Step 2: Insert a New Module

• In the VBA editor, right-click on any of the objects in the Project Explorer window (usually on the left side).
• Choose Insert > Module. This creates a new module for your code.

Step 3: Define the Function

• In the newly created module, type the Function statement to define your UDF. The basic syntax is as follows:

Function MyFunctionName(Param1 As DataType, Param2 As DataType, …) As ReturnType

 ‘ Your code here

End Function

• Replace MyFunctionName with the name of your function, Param1, Param2, etc., with your parameters, DataType with the type of your parameters (e.g., Integer, String), and ReturnType with the type of value your function will return.

Step 4: Write Your Function’s Code

• Inside the function, write the VBA code that performs the calculation or operation you want.

Step 5: Save Your Work

• Press Ctrl + S to save your work. Ensure your Excel workbook is saved as a macro-enabled workbook (.xlsm).

Example: Creating a Simple UDF to Add Two Numbers

Let’s create a UDF named AddNumbers that takes two numbers as input and returns their sum.

1. Follow Steps 1 and 2 to open the VBA editor and insert a new module.

      2. Define the function as follows:

Function AddNumbers(Number1 As Double, Number2 As Double) As Double

AddNumbers = Number1 + Number2

End Function

Save your work and return to Excel.

How to Use Your UDF in Excel

• In Excel, you can now use your UDF like any other function. For example, to use the AddNumbers function, enter =AddNumbers(5, 3) in a cell, and it will return 8.
  
• Creating UDFs in Excel can significantly enhance your productivity by automating repetitive calculations and extending Excel’s functionality to meet your specific needs.