Bloccare inserimento ripetuto di nomi

Private Sub Worksheet_Change(ByVal Target As Range)
If Not Intersect(Target, Range("B11:B20")) Is Nothing Then
    Application.EnableEvents = False
    With Range("B1:B9")
        Set c = .Find(Target.Value, LookIn:=xlValues, lookat:=xlWhole)
        If Not c Is Nothing Then
            Target.Value = ""
            Target.Select
        End If
    End With
    Application.EnableEvents = True
End If
End Sub

Private Sub Worksheet_Change(ByVal Target As Range)
  Set RngRosso = Me.Range("B11:B20")
  Set Rng = Me.Range("B1:B20")
  If Not Intersect(Target, RngRosso) Is Nothing And Target.Count < 2 Then
      With Target
        If Application.CountIf(Rng, .Value) > 1 Then
          MsgBox "nome già esistente"
          .ClearContents
          .Select
        End If
      End With
  End If
  Set Rng = Nothing
Set RngRosso = Nothing
End Sub