将文件另存为xlsx后，工作簿模块中的代码仍然运行

使用VB.NET形式的按钮，.xlsm打开文件并将其另存为.xlsx。保存文件后，不会删除.xlsx文件（Workbook_BeforeClose事件）中的代码，因此，当我要关闭文件时，代码将运行！重新打开文件后，没有代码了。

这是我的VB.NET类：

Imports Excel = Microsoft.Office.Interop.Excel

Public Class Form1
    Dim xlApp As Excel.Application
    Dim xlWorkBook As Excel.Workbook
    Dim xlWorkbooks As Excel.Workbooks

    Private Sub btnSave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSave.Click
        xlApp = New Excel.Application
        xlWorkbooks = xlApp.Workbooks
        xlWorkBook = xlWorkbooks.Open("C:\Temp\testTemplate.xlsm")

        xlApp.DisplayAlerts = False
        xlWorkBook.SaveAs(Filename:="C:\Temp\testTemp.xlsx", FileFormat:=51)  '51=xlOpenXMLWorkbook
        xlApp.DisplayAlerts = True

        xlApp.Visible = True

        'Clean Up
        releaseObject(xlWorkBook)
        releaseObject(xlWorkbooks)
        releaseObject(xlApp)
    End Sub

    Private Sub releaseObject(ByVal obj As Object)
        Try
            System.Runtime.InteropServices.Marshal.ReleaseComObject(obj)
            obj = Nothing
        Catch ex As Exception
            obj = Nothing
        Finally
            GC.Collect()
            GC.WaitForPendingFinalizers()
        End Try
    End Sub
End Class

这在Excel文件的工作簿模块中：

Private Sub Workbook_BeforeClose(Cancel As Boolean)
    MsgBox "event still runs"
End Sub

如何正确保存文件以使其中没有代码？