Private Sub Worksheet_Change(ByVal Target As Range)
If Intersect(Target, Range("F3:F25")) Is Nothing Then Exit Sub 'hors plage, on sort de suite
Target.Offset(, 1) = "": Target.Offset(, 1).Validation.Delete
If Target = 1 Then Target.Offset(, 1).Validation.Add Type:=xlValidateList, _
AlertStyle:=xlValidAlertStop, Operator:=xlBetween, Formula1:="=liste1"
End Sub