Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Address = "$B$2" Then
If Target = "Tous" Then Cells.EntireColumn.Hidden = False: Exit Sub
Application.ScreenUpdating = False
mois_voulu = Application.Match(Target, Range("A3:IV3"), 0)
Range(Cells(3, 3), Cells(3, 256)).EntireColumn.Hidden = True
Range(Cells(3, mois_voulu), Cells(3, mois_voulu + 2)).EntireColumn.Hidden = False
Application.ScreenUpdating = True
End If
End Sub