Private Sub Workbook_NewSheet(ByVal Sh As Object)
    Dim vbc As VBComponent
    Dim cm As CodeModule
    Dim i As Integer
      
    Set vbc = ThisWorkbook.VBProject.VBComponents(Sh.Name)
    Set cm = vbc.CodeModule

    With cm
        i = .CountOfLines +  1 
        .InsertLines i, _
          "Private Sub Worksheet_SelectionChange(ByVal Target As Range)"
        i = i +  1 
        .InsertLines i, _
          "    MsgBox ""A!"", vbInformation"
        i = i +  1 
        .InsertLines i, "End Sub"
    End With

    Set cm = Nothing
    Set vbc = Nothing
End Sub

Public WithEvents App As Application

Private Sub App_SheetChange(ByVal Sh As Object, ByVal Target As Range)
    MsgBox "A"
End Sub

Private Sub App_SheetSelectionChange(ByVal Sh As Object, ByVal Target As Range)
    MsgBox "B"
End Sub

Dim a As New Class1

Private Sub Workbook_Open()
    Set a.App = Application
End Sub