如何在VB中正确将调用的Excel进程关闭？

[twodollars]

我在程序中调用了Excel进行数据处理，但是数据处理后无法将调用的Excel关闭，这是为什么？
Dim OutPutExcel As Object
Dim MainBook As Excel.Workbook

Const ClassObject = "Excel.Application"
Set OutPutExcel = CreateObject(ClassObject)

Set MainBook = OutPutExcel.Workbooks.Open(App.Path & "\" & "ExportWizard.xls")

......

MainBook.SaveAs SaveFile
MainBook.Close
OutPutExcel.Quit
Set OutPutExcel = Nothing
Set MainBook = Nothing
Set MainSheet = Nothing

[of123]

Dim xlApp As Excel.Application
Dim xlBook As Excel.Workbook

' Open the destination Excel workbook.
Set xlApp = New Excel.Application
Set xlBook = xlApp.Workbooks.Open("D:\Book1.xls")
......

' Clean up everything.
xlBook.Save
xlBook.Close False
xlApp.Quit
Set xlBook = Nothing
Set xlApp = Nothing