Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Address = "$S$23" Or Target.Address = "$N$23" Then
If Weekday([S23], vbMonday) = 6 And [N23] = 12 Or Weekday([S23], vbMonday) = 7 And [N23] = 8 Then MsgBox "Selon le règlement interne ...", vbCritical, "Information"
End If
End Sub