I am trying to create a simple message box which will display after I open
the Excel file and if I try to make any change to a document is being made.
If the selection is "Yes" in the messsage box, the change I am making in the
document will be allowed. If the selection is "No" in the message box, the
change will not be allowed. The message box needs to be repeated if I select
"No" and again try to make a change. The message box requirement is really
simple, it just has to say: "Have you updated the dates?" If "Yes", the
change is allowed. If "No", change is not allowed. If after "No", change is
again tried, message box pops up again.

Thanks in advance for your help.