I type the foreign key each time that I enter a record in my layout. In access the foreign key is set automatically when I used a sub form. Does FileMaker has something similar?
It relies on relationship and context. If you have a relationship (parent::primaryKey = child::foreignKey), AND allow creation to records (in child) based on this relationship you are nearly there. Go to the parent record, put a portal on the layout based on the relationship. You should see a blank line as the last row on the portal. If you enter values in the new row, the foreignKey *will* be auto entered.
-- sent from myPhone --
Retrieving data ...