use ppt object in a worker thread

When I create a TPowerPointApplication object in a worker thread's
execute method,like this:
  procedure TMyThread.Execute;
  begin
      FPptApp:=TPowerPointApplication.Create(nil);
      FPptPres:= FPptApp.Presentations.Open(FPptFile,msotrue,1,0);
      FPptPres.SlideShowSettings.Run;
      while not terminated do begin
          sleep(1000);
      end;
      FPptApp.quit;
  end;
Then the ppt start to show. But when I click mouse to move to the next
slide, the ppt window can't response to any event(key or mouse event).
Then I press Ctrl+F2 terminate this program, the ppt window work
again. So how can I resolve this problem?
Thanks.