I ask because I have a table with two field acting as the keys (Var1 and Var2). If I start a new record, type a new number into the combo box containing Var1, and then Tab to the next field (Var2 text box,which is empty) I get an error message saying that Var2 cannot contain a Null value. OTOH, if I just use the ol' mouse to click on the Var2 field, it works fine. Tabbing seems to trigger some sort of check, but there's not code telling it to do that.
It's driving me batty.