主题：在窗口中打印窗口表的数据

帮我看下这段代码有什么问题，我怎么不能打印过期_库存表里面的内容？

Dim Book As New XLS.Book(ProjectPath & "Attachments\过期模板.xls")
Dim fl As String = ProjectPath & "Reports\过期.xls"
Book.Build()
Book.Save(fl)
Dim App As New MSExcel.Application
Dim Wb As MSExcel.WorkBook = App.WorkBooks.Open(fl)
Dim Ws As MSExcel.WorkSheet = Wb.WorkSheets(1)
App.Visible = True
ShowAppWindow("过期_库存表",2)
Ws.PrintPreview
App.Quit