Private Sub Worksheet_Change(ByVal Target As Range)
Application.EnableEvents = False 'désactive les évènements
[A2].Validation.Delete 'RAZ
If [A1] = [D1] Then
[A2] = [D1]
Else
[A2].Validation.Add xlValidateList, Formula1:="=" & [K2:K5].Address
If Application.CountIf([K2:K5], [A2]) = 0 Then [A2] = ""
End If
Application.EnableEvents = True 'réactive les évènements
End Sub