public function insertNewRowBefore($pBefore = 1, $pNumRows = 1)
    {
        if ($pBefore >= 1) {
            $objReferenceHelper = PHPExcel_ReferenceHelper::getInstance();
            $objReferenceHelper->insertNewBefore('A' . $pBefore, 0, $pNumRows, $this);
        } else {
            throw new PHPExcel_Exception("Rows can only be inserted before at least row 1.");
        }
        return $this;
    }