Form calls the user edit routine with the type parameter equal to U_BEGINFORM each time a complete form is displayed on the screen. This is done whenever a new form is put on the screen, when the current form is cleared, or a new record is displayed. The old_value and new_value parameters point to the name of the current form. The other parameters are NULL. The user edit routine is called after the form has been displayed and the field values set. If the user edit routine returns an error message, form displays the error message at the bottom of the screen, and form continues. This call allows the user edit routine to do any additional field initializations it desires each time a new record is displayed.
U_BEGINFORM only occurs when the form or data record changes; for example, it does not happen after the operator presses the REFRESH key.