INT B3 - ZIPKEY - PLAY BACK EXIT KEY FOR ENTRY WITH GIVEN ZIPCODE
        AH = 77h
        DX = zipcode region (0-999)
        CH = last two digits of zipcode (0-99)
        BX = 16-bit BIOS keycode for a defined ZIPKEY alternate exit key
Return: CF set on error
            AX destroyed
        CF clear if successful
            zipcode specification as defined by the BX keystroke is placed in
              keyboard buffer, as if the user had popped up ZIPKEY and exited
              by pressing the key specified by BX