I was thinking about this... I would figure it would be safer, especially with cookies enabled, if any "request" to the database for records from anyone with "edit" powers set the "Admin_Last_Edit" datetime field to the current time, and return that to the form.

Then, if the time does not match the time in the record, you know for sure something has changed.

It's much safter than simply using a "later than" type of time flag.