This is some code that I ran across that will let you know the error code for the particular error. This is extremely useful when you want to change/override the error message associated with it.

Private Sub Form_Error(DataErr As Integer, Response As Integer)
MsgBox "Error#: " & DataErr ' Display the error number
Response = acDataErrDisplay ' Display Default message
End Sub

This is just things that people may type into a search engine to try to find code so you can just ignore this now...

error checking, error number, error #, override error message, default error message, change error message