Public LastRow As Long
Function My_Func() As String
  Application.Volatile
End Function

Private Sub Workbook_Open()
  LastRow = Worksheets("Лист1").UsedRange.Row _
    + Worksheets("Лист1").UsedRange.Rows.Count
End Sub

Private Sub Worksheet_Calculate()
  If LastRow < Worksheets("Лист1").UsedRange.Row _
    + Worksheets("Лист1").UsedRange.Rows.Count _
  Then
    MsgBox "Вставили " & Worksheets("Лист1").UsedRange.Row _
      + Worksheets("Лист1").UsedRange.Rows.Count - LastRow _
      & " строк/у/и)"
  End If
  If LastRow > Worksheets("Лист1").UsedRange.Row _
    + Worksheets("Лист1").UsedRange.Rows.Count _
  Then
    MsgBox "Удалили " & LastRow - (Worksheets("Лист1").UsedRange.Row _
      + Worksheets("Лист1").UsedRange.Rows.Count) _
      & " строк/у/и)"
  End If
  LastRow = Worksheets("Лист1").UsedRange.Row _
    + UsedRange.Rows.Count
End Sub