Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Address <> "$AB$4" Then Exit Sub
ActiveSheet.Range("AY7").Validation.Delete
For n = 9 To Sheets("LISTES").Cells(2, Columns.Count).End(xlToLeft).Column
If InStr(Sheets("LISTES").Cells(2, n), Target.Value) <> 0 Then
derlin = Sheets("LISTES").Cells(Rows.Count, n).End(xlUp).Row
form = "=LISTES!" & Cells(3, n).Address & ":" & Cells(derlin, n).Address
ActiveSheet.Range("AY7").Validation.Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:= _
xlBetween, Formula1:=form
End If
Next
End Sub