>The user is logged in for a particular site (i.e. A) and wants to change all values except the site code. In a from I can find the record, When I try to change the I get an error message that the uniqueness of the record is violated. I use the UPDATE command. Is there a may of updating the record or do I have to tell the user to log on with that site (my current statutory)?

See if you have an empty deleted record in this table in addition to Ed's suggestion. Pack the table if this is the case (requires exclusive access).