Tim,

Are you trying to make *sure* that no one else can read records that another user is editing? Because if not, you might be able to get away with simply allowing the current user to overwrite the records ala VFP's

=TABLEUPDATE(.T., .T.)

If you really need to control access, you consider a stored procedure on the backend server that consults and populates a Keys_In_Use table before returning records. (you can utilize a timestamp field to recurringly wipe out entries older than a decided-upon timeout period, as well as a client identifier that clears out old entries upon each new request)

HTH,

-Bernie