Thanks Trevor,
It seems to be updating the first field (i.e. FirstName) only.
The SQL for the Combo row source is
SELECT tblMaster.ID, tblMaster.Network, tblMaster.FirstName, tblMaster.LastName, tblMaster.Title, tblMaster.Address1, tblMaster.Address2, tblMaster.Address3, tblMaster.City...