private function writeRecalcId()
    {
        $record = 0x01C1; // Record identifier
        $length = 8; // Number of bytes to follow

        $header = pack('vv', $record, $length);

        // by inspection of real Excel files, MS Office Excel 2007 writes this
        $data = pack('VV', 0x000001C1, 0x00001E667);

        return $this->writeData($header . $data);
    }