VB中怎么关闭Powerpoint

VB中如何关闭Powerpoint?
在PowerPoint的模块中可用Application.Quit关闭它，但把这代码放入VB的过程中就不能关闭，代码如下：
Dim PPT As powerpoint.Presentation
Set PPT = GetObject(App.Path & "\PowerPoint.PPT")
PPT.Application.Visible = True
PPT.Application.DisplayAlerts = False
PPT.Application.Quit
请高手指教！

[解决办法]
这个代码在我这里通过了

VB code

Private Sub Command1_Click()    Dim pptapp As New PowerPoint.Application    Dim ppt As PowerPoint.Presentation    Set ppt = GetObject("C:\pp.PPT")    pptapp.Visible = msoCTrue    ppt.Save    ppt.Close    pptapp.QuitEnd Sub