[Joemully]

Hi - I've set up a simple database for some survey work. Data tables are linked by a primary key consisting of a 10 to 12 digit location code (picked up from a drop-down list) and a 2 digit survey number - all stored as text. Rather than use compound relationships I would like to combine these into a single primary key.
I know calculated fields in tables are wicked...! but how can do I do this automatically in ACCESS 2007. I can combine the two easilly in a calculated control in a form.... but not directly into the primary field. Although the result does appear in the control - I get an error message telling me I can't have a null entry in the primary field. Do I need to set up an event procedure???? Thoughts much appreciated