Ususally Key fields are a serialized number. This is prefered for a few reasons. Its computer generated so there would be no typos. If you have typos in your key field then you can get cross-linked records. The purpose of key fields is so you don't need the fields in both tables, which saves on space and speeds up the app. Calculation are based on the table occurance you are using which is another reason not to use a key field as you are. I would suggest changing to the serialized. The primary key is the only key generated the foreign key is not. The foreign is assigned when you create a new record from a portal or you would setup a popup menu or drop down list to link the records.