Private Sub Worksheet_SelectionChange(ByVal Target As Range)
    Select Case Target.Address
            Case Range("A1").Address
                Range("B1") = 1
            Case Range("A2").Address
                Range("B2") = 2
    End Select
End Sub

    For intVBComponent = 1 To ioobjExcel.VBE.VBProjects("VBAProject").VBComponents.Count
        If ioobjExcel.VBE.VBProjects("VBAProject").VBComponents(intVBComponent).Name = "ThisWorkbook" Then
            With ioobjExcel.VBE.VBProjects("VBAProject").VBComponents(intVBComponent).CodeModule
               .DeleteLines 1, .CountOfLines
               .AddFromString "Option Explicit"
               .AddFromString vbCrLf
               .AddFromString "Private Sub Workbook_Open()" & vbCrLf & _
               "    ThisWorkbook.Application.Calculation = xlCalculationManual" & vbCrLf & _
               "End Sub"
            End With
        End If
    Next intVBComponent