public function set_v_align($location) {
        switch ($location) {
            case 'top':
                $this->format['alignment']['vertical'] = PHPExcel_Style_Alignment::VERTICAL_TOP;
                break;
            case 'vcentre':
            case 'vcenter':
            case 'centre':
            case 'center':
                $this->format['alignment']['vertical'] = PHPExcel_Style_Alignment::VERTICAL_CENTER;
                break;
            case 'vjustify':
            case 'justify':
                $this->format['alignment']['vertical'] = PHPExcel_Style_Alignment::VERTICAL_JUSTIFY;
                break;
            default:
                $this->format['alignment']['vertical'] = PHPExcel_Style_Alignment::VERTICAL_BOTTOM;
        }
    }