如何隐藏powerpoint 窗体(100分)

这句话ppt.Visible:=true;不能改成 ppt.Visible:=falsed的
try
ppt:= CreateOleObject('PowerPoint.Application');
ppt.Visible:=true;
Dc:=ppt.Presentations.Open(FileName,msoFalse, msoFalse, msoTrue); //msoFalse, msoFalse, msoFalse
Dc.SaveAs(HtmFilePath,ppSaveAsHTMLv3,msoTrue); //ppSaveAsHTML
// ppt.ActivePresentation.SaveAs(HtmFilePath,ppSaveAsHTMLv3,msoTrue); //ppSaveAsHTML
Sleep(500);
finally
ppt.quit;
end;