private function writeDimensions()
    {
        $record = 0x0200; // Record identifier

        $length = 0x000E;
        $data = pack('VVvvv', $this->firstRowIndex, $this->lastRowIndex + 1, $this->firstColumnIndex, $this->lastColumnIndex + 1, 0x0000); // reserved

        $header = pack('vv', $record, $length);
        $this->append($header . $data);
    }