Let's say I've a Form with an unbound TextBox which must first receive a value in order to trigger "visiblity=True" for the Form's next data control. This is because in the normal course this field must have a value to become part of the criteria for a pending function.

In such chases, I've been providing its TextBox's "ON LOST FOCUS" Event with something akin to "If not isnull(x_textBoxName). . ."

I'm looking for a better Event for this sort of chequepoint because, should I happen to be in "x_textBoxName" when I opt to do anything else - say close the Form - my code no longer simply performs the desired blockage of proceeding without the data entry, but actually prevents execution of the close request. I think I use a "Ctrl-F4" by instinct.

Any more acceptable practice? Thanks.