protected function _setDuplicatedField( $oPayment, $sFieldName, $sType, $aParams, $sField )
    {
        $mValue = $aParams[$sField];
        settype( $mValue, $sType );

        if ( ( $sFieldName == 'oxaddsumtype' ) and !in_array( $mValue, array('abs', '%') ) ) {
            return false;
        }

        $oPayment->$sField = new oxField( $mValue );

        return true;
    }