Option Explicit
Private Sub Workbook_SheetActivate(ByVal Sh As Object)
If Cells(1, 1) > DateSerial(Year(Cells(3, 2)), Month(Cells(3, 2)) + 1, 0) Then
Range("A1:L200").Value = Range("A1:L200").Value
Cells(1, 1) = DateSerial(Year(Cells(3, 2)), Month(Cells(3, 2)) + 1, 0)
Cells(1, 3) = ""
End If
End Sub