var coup1="ARK2010";
var coup2="happy2010";

function CalculateOrder(form) {

 if (form.text1.value == coup1)
 {
 form.discount_rate.value = "20";
 form.discount_rate2.value = "20";
 form.on0.value = "ARK2010";
 form.os0.value = "happy2010 - Discount 20%";
 }

  if (form.text1.value == coup2)
 {
 form.discount_rate.value = "20";
 form.discount_rate2.value = "20";
 form.on0.value = "happy2010";
 form.os0.value = "ARK2010 - Discount 20%";
 }
}