Form calls the user edit routine with the type parameter equal
to U_ENDVAL every time the operator presses the RETURN key in a validation
form to return to the original form. The old_value parameter points to
the name of the validation form, and the new_value parameter points to
the name of the original form. The exit_char parameter contains the form
number of the original form. The edit_name parameter is NULL. The return
value from your user edit routine is ignored.