private function _writeRangeProtection()
	{
		foreach ($this->_phpSheet->getProtectedCells() as $range => $password) {
			// number of ranges, e.g. 'A1:B3 C20:D25'
			$cellRanges = explode(' ', $range);
			$cref = count($cellRanges);

			$recordData = pack(
				'vvVVvCVvVv',
				0x0868,
				0x00,
				0x0000,
				0x0000,
				0x02,
				0x0,
				0x0000,
				$cref,
				0x0000,
				0x00
			);

			foreach ($cellRanges as $cellRange) {
				$recordData .= $this->_writeBIFF8CellRangeAddressFixed($cellRange);
			}

			// the rgbFeat structure
			$recordData .= pack(
				'VV',
				0x0000,
				hexdec($password)
			);

			$recordData .= PHPExcel_Shared_String::UTF8toBIFF8UnicodeLong('p' . md5($recordData));

			$length = strlen($recordData);

			$record = 0x0868;		// Record identifier
			$header = pack("vv", $record, $length);
			$this->_append($header . $recordData);
		}
	}