private function writeCalcPr(XMLWriter $objWriter, $recalcRequired = true)
    {
        $objWriter->startElement('calcPr');

        //    Set the calcid to a higher value than Excel itself will use, otherwise Excel will always recalc
        //  If MS Excel does do a recalc, then users opening a file in MS Excel will be prompted to save on exit
        //     because the file has changed
        $objWriter->writeAttribute('calcId', '999999');
        $objWriter->writeAttribute('calcMode', 'auto');
        //    fullCalcOnLoad isn't needed if we've recalculating for the save
        $objWriter->writeAttribute('calcCompleted', ($recalcRequired) ? 1 : 0);
        $objWriter->writeAttribute('fullCalcOnLoad', ($recalcRequired) ? 0 : 1);

        $objWriter->endElement();
    }