public function GetDiscountValue()
    {
        $dValue = 0;
        $iTmpPointer = $this->getItemPointer();
        $this->GoToStart();
        while ($oDiscount = $this->Next()) {
            $dValue += $oDiscount->GetValue();
        }

        $this->setItemPointer($iTmpPointer);

        return $dValue;
    }