On Error GoTo LineLabel

This statement lets you provide a custom error handler.

Public Sub MySubroutine() 
   On Error GoTo ErrorHandler 


   Exit Sub 
ErrorHandler: 
   Call MsgBox(Err.Number & " - " & Err.Description) 
End Sub 

The LineLabel must be in the same procedure as the On Error statement.
You should always put this LineLabel at the end of the subroutine.
This section of code between the LineLabel and the End Sub is often referred to as the Error Handling Routine.
You should always include an Exit Sub, Exit Function or Exit Property before your error handling routine to ensure that it is only executed when an error occurs.

Nested Subroutines