DebugだとExcelが終了しない

Public Class Form1
 ＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿
|　Windows フォーム デザイナで生成されたコード |
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    Private Sub Button1_Click(...) Handles Button1.Click
        Dim stReturn As String = CMakeFile.NewEx()

        MessageBox.Show(stReturn)
    End Sub

End Class

Public Class CMakeFile 

    Public Shared Function NewEx() As String
        Dim xlApp As New Excel.Application()

        Try
            Dim xlBooks As Excel.Workbooks = xlApp.Workbooks

            Try
                Dim xlFilePath As String = "D:\\test.xls"
                Dim xlBook     As Excel.Workbook = xlBooks.Open(xlFilePath)

                Try
                    Dim xlSheets As Excel.Sheets = xlBook.Worksheets

                    Try
                        Dim xlSheet As Excel.Worksheet = DirectCast(xlSheets(1), Excel.Worksheet)

                        Try
                            Dim xlCells As Excel.Range = xlSheet.Cells                    

                            Try
                                Dim xlRange1 As Excel.Range = DirectCast(xlCells(1, 12), Excel.Range)

                                Try
                                    xlRange1.Value = "テストデータ"
                                Finally
                                    If Not xlRange1 Is Nothing Then
                                        System.Runtime.InteropServices.Marshal.ReleaseComObject(xlRange1)
                                    End If
                                End Try
                            Finally
                                If Not xlCells Is Nothing Then
                                    System.Runtime.InteropServices.Marshal.ReleaseComObject(xlCells)
                                End If
                            End Try

                            Dim strNewFile As String = "D:\\test_tmp.xls"

                            xlApp.DisplayAlerts = False
                            xlSheet.SaveAs(strNewFile)
                            xlApp.DisplayAlerts = True

                            Return strNewFile
                        Finally
                            If Not xlSheet Is Nothing Then
                                System.Runtime.InteropServices.Marshal.ReleaseComObject(xlSheet)
                            End If
                        End Try
                    Finally
                        If Not xlSheets Is Nothing Then
                            System.Runtime.InteropServices.Marshal.ReleaseComObject(xlSheets)
                        End If
                    End Try
                Finally
                    If Not xlBook Is Nothing Then
                        Try
                            xlBook.Close()
                        Finally
                            System.Runtime.InteropServices.Marshal.ReleaseComObject(xlBook)
                        End Try
                    End If
                End Try
            Finally
                If Not xlBooks Is Nothing Then
                    Try
                        xlBooks.Close()
                    Finally
                        System.Runtime.InteropServices.Marshal.ReleaseComObject(xlBooks)
                    End Try
                End If
            End Try
        Finally
            If Not xlApp Is Nothing Then
                Try
                    xlApp.Quit()
                Finally
                    System.Runtime.InteropServices.Marshal.ReleaseComObject(xlApp)
                End Try
            End If
        End Try
    End Function

End Class