Here  https://msdn.microsoft.com/en-us/library/windows/desktop/ms675299(v=vs.85).aspx I read about: As I understand when I use: #include <MsgBoxConstants.au3> Example() Func Example() ; Error monitoring. This will trap all COM errors while alive. ; This particular object is declared as local, meaning after the function returns it will not exist. Local $oErrorHandler = ObjEvent("AutoIt.Error", "_ErrFunc") ; some ADO STUFF ; .....