Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Column <> 1 Or Target.Count <> 1 Then Exit Sub
With Target.Offset(, 1)
.Validation.Delete
If Target.Value = "A" Then
.Value = "Ok"
Else
.Validation.Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:=xlBetween, Formula1:="=Test_liste"
End If
End With
End Sub