Dim app As New Excel.Application
        Dim pfad As String = "C:\tmp\foobar.xls"
        Dim book As Excel.Workbook = Nothing
 
        '// load
        With app
            book = .Workbooks.Open(pfad)
            .Visible = True
            System.Threading.Thread.Sleep(3000)
        End With
 
        '// kill
        book.Close()
        app.Quit()
        Marshal.ReleaseComObject(app)
        Marshal.ReleaseComObject(book)
        book = Nothing
        app = Nothing
        GC.Collect()
        GC.WaitForPendingFinalizers()
        GC.Collect()
        GC.WaitForPendingFinalizers()