Excel VBA : How to debug a user defined function (UDF)

Deepanshu Bhalla 4 Comments ,

In VBA, the best way to debug a user defined function (UDF) is by writing a temporary Sub procedure that calls your function and then step into the Sub procedure by pressing F8 key.

VBA: How to debug a user defined function (UDF)

Example :
User Defined Function (UDF)

Let's say you have the following function. This function calculates a grade based on the values of these scores. It takes two parameters: "score" and "score1".

Function grade(score As Single, score1 As Single) As String
         If score >= 75 And score1 >= 75 Then
         grade = "A"
         ElseIf score > 50 And score1 > 50 Then
         grade = "B"
         grade = "C"
         End If
End Function
Step 1: Temporary Sub Procedure

You create a Sub procedure within the same module where your function is defined. This Sub procedure will call your UDF with specific inputs. By using a Sub procedure, you can easily run and debug your function.

Sub test()
MsgBox grade(Range("A2").Value, Range("B2").Value)
End Sub
Step 2: Step Into (F8 Key)

Position your cursor before Sub test() and then press F8 key to step into the Sub Procedure.

How to debug function in VBA
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About Author:
Deepanshu Bhalla

Deepanshu founded ListenData with a simple objective - Make analytics easy to understand and follow. He has over 10 years of experience in data science. During his tenure, he worked with global clients in various domains like Banking, Insurance, Private Equity, Telecom and HR.

Post Comment 4 Responses to "Excel VBA : How to debug a user defined function (UDF)"
  1. Perfect and simple solution. Thanks. Gary

  2. Thanks - this was helpful!

  3. Stepping into my function as described works, but calling it from the spreadsheet throws a #Name? error. Confused on why it would work if I step into it but not when I call it from a cell?

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