function validate(theform) {
   var valid=true;
   var message = '';

   if (theform.first_name.value == "") {
      valid = false;
      message += 'First Name; ';
   }
   if (theform.last_name.value == '') {
      valid = false;
      message += 'Last Name; ';
   }
   if (theform.amount.value == '') {
      valid = false;
      message += 'Payment Amount; ';
   }
   if (theform.currency_code.options[0].selected) {
      valid = false;
      message += 'Currency; ';
   }
   if (theform.item_name.value == '') {
      valid = false;
      message += 'Invoice/Description; ';
   }

   if (valid) return true;
   else {
      alert("Please complete all fields.\n\nYou missed the following fields:\n\n" + message);
      return false;
   }
}