I wrote a program in vb.net 2005 to open a spread sheet, read data and then
close the spreadsheet. The probelm is it is not really closing.  

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

'  OPEN WORKSHEET AND DO STUFF

           xlBook.Application.Visible = True
           xlBook.Windows(1).Visible = True
           xlBook.Application.WindowState = Excel.XlWindowState.xlMinimized

           '            Call loadSheet(xlbook.Worksheets(SheetName))

           xlBook.Close(True)
           xlApp.Quit()
           NAR(xlBook)
           NAR(xlApp)

     

Private Sub NAR(ByVal o As Object)
       Try
           System.Runtime.InteropServices.Marshal.ReleaseComObject(o)
       Catch ex As Exception
       Finally
           o = Nothing
       End Try
   End Sub

Can someone tell me what I am doing wrong?