DateDiff, MS Access 2000

Can anyone explain how DateDiff is used. I developed a form from my table. I have two date/time fields – “DEPART” and “RETURN”. I created another field called “DAYS DEPLOYED”. In the “DAYS DEPLOYED” field’s properties, I inserted the following: =DateDiff(“d”,[DEPART],[RETURN]) When I fill out the form, the “DAYS DEPLOYED” field is populated as expected; however, the results do not appear in the table, which in turn generates a false Report. Can anyone shed any light on this.

Thanks
Jack Purcell