public function Form()
 {
     $form = parent::Form();
     if ($this->VariableAmount) {
         $form->setSaveableFields(array("UnitPrice"));
         $form->Fields()->push($giftamount = new CurrencyField("UnitPrice", "Amount", $this->BasePrice));
         $giftamount->setForm($form);
     }
     $form->setValidator($validator = new GiftVoucherFormValidator(array("Quantity", "UnitPrice")));
     return $form;
 }