Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Count > 1 Then Exit Sub
If Not Intersect(Target, [A1]) Is Nothing Then
Select Case Target.Value
Case Is = 1: Feuil2.Visible = xlSheetVisible: Feuil3.Visible = xlSheetVisible
Case Is = 2: Feuil2.Visible = xlSheetVisible: Feuil3.Visible = xlSheetHidden
Case Is = 3: Feuil2.Visible = xlSheetHidden: Feuil3.Visible = xlSheetHidden
End Select
End If
End Sub