How to Create User Defined Function in Microsoft Excel

Microsoft Excel has numerous built-in functions that perform different mathematical, logical or text operations. However, situations may arise where the built-in functions in Excel are not enough or does not precisely match your requirements, and that’s where user-defined functions or UDF comes into play.

User-defined functions (UDFs) are defined by users to meet their specific requirements. These functions are custom functions that can perform multiple operations beyond the built-in Excel functions. In this article, we will learn how to write and create User Defined Functions in Microsoft Excel.

Step 1: Launch the Visual Basic Editor

To create a user-defined function, the first thing you need to do is launch the Visual Basic Editor. The shortcut key to launch the Visual Basic Editor is “ALT+F11” on Windows, while on Mac it is “FN+ALF+F11”. Alternatively, you can follow the steps below:

1. Open Microsoft Excel
2. Click on the Ribbon and select Developer option
3. In the Code Group, click on the Visual Basic button to launch the VBE

Step 2: Creating a New Module

Once the Visual Basic Editor is launched, you need to create a new module. You can create a new module by either clicking on the “Insert” menu and selecting “Module,” or by pressing “ALT+I+M”. Alternatively, you can choose “Module” from the “Insert” menu. A new module will be created in the project library.

Step 3: Writing the User-Defined Function

Now it’s time to write the function code. In this step, you give a name to your function and define its argument’s data type. Below is the syntax for creating a new user-defined function:

Function [function_name] ([arguments]) As [Datatype]
    [VBA code]
    [function_name] = [Return Values]
End Function

Here we can write the function_name, arguments, VBA code, and the return value. If you need to define multiple arguments, you separate each argument with a comma. Let’s write a simple example:

'User-Defined Function to Add Two Numbers

Function Add (Num1 As Double, Num2 As Double) As Double

Add = Num1 + Num2

End Function

In this example, we have created a user-defined function named “Add,” that has two arguments: Num1 and Num2 of double datatype. We’ve defined the VBA code for this function as adding these two arguments and storing it as the return value.

Step 4: Save the Module

After writing the function code, you save the module in VBA editor. In the VBA editor, click on “File” from the menu and select the “Save” option. Alternatively, you can press “CTRL + S”. The module will be saved as a .bas file.

Step 5: Using the User-defined function

Now that we have created the user-defined function for adding two numbers, it’s time to use it in Microsoft Excel.

1. Open Microsoft Excel sheet
2. Click on a cell and enter the formula,

=ADD(A1,B1)

In this example, A1 and B1 cells contain values you want to add. When you press “Enter,” this function will call the “Add” UDF and perform the calculation.

Conclusion

As we have seen, User-defined functions are easy to write and customize and can perform multiple operations beyond the built-in Excel functions. With a basic understanding of Visual Basic for Applications (VBA), creating user-defined functions can help simplify and automate complex calculations in Excel.