I would do everything in batches.

Send your data sets back to the server in XML, then convert to cursor. Scan cursor recieved from client: (1) if no primary key, a new record was added. Add key then do an insert. (2) For deletes, use an extra field that indicates a deleted record. If field is flagged, delete from underlying table (3) If record has primary key and no delete flad, it's an update. Update underlying table. Put all this into a single SCAN ENDSCAN loop.

To reject updates while another person is editing, use a some sort of timestamp to see who got to record first.

Charlie