Private Sub Workbook_SheetActivate(ByVal Sh As Object)
Dim nSheets, s As Object, liste$
If Sh.Name <> "Feuil1" Then Exit Sub
nSheets = Array("Feuil1", "Feuil3")
For Each s In Me.Sheets
If IsError(Application.Match(s.Name, nSheets, 0)) Then liste = liste & "," & s.Name
Next
With Sh.[B6].Validation
.Delete
If liste <> "" Then .Add xlValidateList, Formula1:=Mid(liste, 2)
End With
End Sub