taken from the help file

DisplayAlerts Property
See Also Applies To Example Specifics
True if Microsoft Excel displays certain alerts and messages while a
macro is running. Read/write Boolean.

Remarks
The default value is True. Set this property to False if you don't
want to be disturbed by prompts and alert messages while a macro is
running; any time a message requires a response, Microsoft Excel
chooses the default response.

If you set this property to False, Micorosoft Excel sets this property
to True when the code is finished, unless you are running cross process
code.

When using the SaveAs method for workbooks to overwrite an existing
file, the 'Overwrite' alert has a default of 'No', while the 'Yes'
response is selected by Excel when the DisplayAlerts property is set
equal to True.

Example
This example closes the workbook Book1.xls and doesn't prompt the
user to save changes. Any changes to Book1.xls aren't saved.

Application.DisplayAlerts = False
Workbooks("BOOK1.XLS").Close
Application.DisplayAlerts = True
This example suppresses the message that otherwise appears when you
initiate a DDE channel to an application that's not running.

Application.DisplayAlerts = False
channelNumber = Application.DDEInitiate( _
   app:="WinWord", _
   topic:="C:\WINWORD\FORMLETR.DOC")
Application.DisplayAlerts = True
Application.DDEExecute channelNumber, "[FILEPRINT]"
Application.DDETerminate channelNumber
Application.DisplayAlerts = True

Graham

Sub SheetDelete()
   Application.DisplayAlerts = False
   ActiveWindow.SelectedSheets.Delete
   Application.DisplayAlerts = True
End Sub

Gord Dibben  MS Excel MVP