主题：[求助],请帮看看这段代码的打开excel应用程序怎么自动关闭

以下这段代码运行后启动excel程序不能自动关闭，求关闭的方法

Dim Book As New XLS.Book(ProjectPath & "Attachments\明细.xls")
Dim fl As String = ProjectPath & "Reports\明细.xls"
Book.Build() '生成细节区
Dim Sheet As XLS.Sheet = Book.Sheets(0) '引用工作簿的第一个工作表
Dim a As  Integer
a=sheet.Rows.Count '取得总行数
Dim aa As Integer
For aa=1  To a
Sheet.Rows(aa).PageBreak=False
Next
Dim i As Integer
Dim x As  Double
Dim t As Integer
Dim y As Integer
y=20 '定义除表头之外的打印行数
x=Math.Floor((a-4)/y)
For t=1 To x
Sheet.Rows(t*y+4).PageBreak = True
Next
Book.Save(fl) ' 保存工作簿

Dim App As New MSExcel.Application
App.Visible = False
Dim Wb As MSExcel.WorkBook = App.WorkBooks.Open(ProjectPath & "Reports\明细.xls")
Dim Ws As MSExcel.WorkSheet = Wb.WorkSheets(1)
With Ws.PageSetup
   .PrintTitleRows =Ws.Rows("2:5").Address
End With

Dim Proc As New Process '打开工作簿
Proc.File = fl
Proc.Verb = "Print" '指定动作
Proc.Start()

谢谢，果真如此