User Level Security of course (so you can differentiate users).
An RWOP query with
WHERE UserID = CurrentUser()
(UserID being the user you would need to store in the table by Before_Update
code or something)
An RWOP query would PREVENT them seeing other records (I think). Maybe that's
not what you want. Also, an RWOP query isn't necessarily that secure anyway.
If your customer is not full of smart hackers, you might just as well put the
WHERE clause in the Recordsource query of a form.
If you want them to see all records but only be able to update their own ones,
I suppose you would trap the Before_Update event and reject it (though that
would seem unacceptably "late" to me). On some forms, I run through the text
boxes making them read-only or not, or hide buttons or something, depending. A
bit of code, but never mind. On_Current can be used to detect
change-of-viewed-record, if I recall.
Chris