怎么让phpexcel生成的excel文件打开时需要密码

$objPHPExcel=new PHPExcel();
$objPHPExcel->getSecurity()->setLockWindows(true);
$objPHPExcel->getSecurity()->setLockStructure(true);
$objPHPExcel->getSecurity()->setWorkbookPassword("abc");
$objWriter=new PHPExcel_Writer_Excel5($objPHPExcel);
$objWriter->setTempDir(".");
$objWriter->save("abc.xls");