Is it possible to Time stamp a sheet to indicate everytime a worksheet has
been opened?

I have a file which users should be using daily, but I suspect they are not
(although they tell me they are!) so I was wondering if I could build a
database within that file that would timestamp an area of a worksheet every
time the file was actually opened (as opposed to everytime it was saved, as
they might not have to save it everytime), say A1 in Sheet1, so the second
time they access/open the file in would stamp A2 in Sheet1 etc etc

Hope someone can help