public function countVouchers()
    {
        $aStatus = [];

        $oDb = \OxidEsales\Eshop\Core\DatabaseProvider::getDb();
        $sQuery = 'select count(*) as total from oxvouchers where oxvoucherserieid = ' . $oDb->quote($this->getId());
        $aStatus['total'] = $oDb->getOne($sQuery);

        $sQuery = 'select count(*) as used from oxvouchers where oxvoucherserieid = ' . $oDb->quote($this->getId()) . ' and ((oxorderid is not NULL and oxorderid != "") or (oxdateused is not NULL and oxdateused != 0))';
        $aStatus['used'] = $oDb->getOne($sQuery);

        $aStatus['available'] = $aStatus['total'] - $aStatus['used'];

        return $aStatus;
    }