Sometimes the application displays a messagebox asking if the user wants to continue,
if he/she wants to save a file before closing, or want some other verification from the user.
These messages can be turned off by using this command in a macro :
Application.DisplayAlerts = False
The warningmessages will remain turned off until you enable them again with this command:
Application.DisplayAlerts = True
If you just want to close a workbook without the user being prompted for any confirmations about saving
the workbook you can simply do this:
ActiveWorkbook.Close False ' closes the active workbook without saving any changes
ActiveWorkbook.Close True ' closes the active workbook and saves any changes