computing 2 value and adding it..

I have a 2 form value on 500/pcs and 1000/pcs And i was hoping how will i compute this when i comes to this code.. --- start -------------------- $final_price_usmail = ( $bcard_price + $usmail_price ); $final_price_courier = ( $bcard_price + $courier_price ); if ($v_sendvia === 'USMail') { echo '$' . $bcard_price . ' (Business Card) + ' . $usmail_price . ' (U.S. Mail) = $' . $final_price_usmail . '.00'; } elseif ($v_sendvia === 'Courier') { echo '$' . $bcard_price . ' (Business Card) + ' . $courier_price . ' (Courier) = $' . $final_price_courier . '.00'; } --- end -------------------- Im looking for a way that when the user click on the 1000/pcs it will compute * 2. But i couldt figure this out.. -- Thank you, Louie Miranda (louie@axishift.ath.cx)