Trap Those Errors
This is the conventional way of trapping errors as your VBA code runs.
This method always displays a dialog box with the error message.
As I run my code and find out how to handle each error, I change the code to tell me what I should have done.
See also my example for skipping past errors and simply writing them to a log for later retrieval.
Module is already in progress
On Error GoTo ErrHandler
'Tell VBA to use your trapping routine
Module continues then
Selection.Value = 123
Exit Sub 'You must exit the sub or the
'Error Handler is invoked
'everytime you come to the end of the macro
ErrHandler:
Select Case Err
'Err is already defined in Excel to hold the
'numeric code for errors
Case 91
MsgBox "There is no active cell"
Case 1000
MsgBox "Cannot assign a value to the selection."
Case 1004
MsgBox Err & " " & Error(Err) & Chr(13) & Chr(13) _
& "The method you specified cannot be used on the object."
Case 1005
MsgBox "The worksheet is protected."
Case Else
MsgBox Error(Err) & err.number & err.description
End Select
End Sub