XL 2010 supprimer les lignes doubles en gardant original code VBA

Sub test()
Dim der&
   With Sheets("Feuil1")
      If .FilterMode Then .ShowAllData
      der = .Cells(Rows.Count, "a").End(xlUp).Row
      Application.ScreenUpdating = False
      .Columns(1).Insert: On Error GoTo Fin
      .Range("a1:a" & der).Formula = "=row()"
      .Range("a1:a" & der) = .Range("a1:a" & der).Value
      .Range("a1:d" & der).Sort key1:=Range("b1"), order1:=xlDescending, _
             key2:=Range("a1"), order2:=xlDescending
      .Range("a1:d" & der).RemoveDuplicates Columns:=Array(2)
      .Range("a1:d" & der).Sort key1:=Range("a1"), order1:=xlAscending
Fin:
      .Columns(1).Delete
   End With
End Sub