Application.Interactive = False
' Do necessary calculations / processing
Application.Interactive = True
Application.Interactive is True if Microsoft Excel is in interactive mode; this property is usually True. If you set the this property to False, Microsoft Excel will block all input from the keyboard and mouse (except input to dialog boxes that are displayed by your code). Blocking user input will prevent the user from interfering with the macro as it moves or activates Microsoft Excel objects. Read/write Boolean.
This property is useful if you're using DDE or OLE Automation to communicate with Microsoft Excel from another application.
If you set this property to False, don't forget to set it back to True. Microsoft Excel won't automatically set this property back to True when your macro stops running.