private function writeFileVersion(XMLWriter $objWriter)
    {
        $objWriter->startElement('fileVersion');
        $objWriter->writeAttribute('appName', 'xl');
        $objWriter->writeAttribute('lastEdited', '4');
        $objWriter->writeAttribute('lowestEdited', '4');
        $objWriter->writeAttribute('rupBuild', '4505');
        $objWriter->endElement();
    }