XL 2021 Identifier lignes des doublons dans message Box

Private Sub CommandButton1_Click()
    Dim i As Long
    Dim j As Long
    Dim lastRow As Long
    Dim doublons As String
    Application.ScreenUpdating = False
    lastRow = ActiveSheet.Range("B" & Rows.Count).End(xlUp).Row

    For i = 5 To lastRow
        For j = i + 1 To lastRow
            If UCase(Cells(i, 2).Value) = UCase(Cells(j, 2).Value) Then
                doublons = doublons & "Ligne " & i & " et ligne " & j & vbCrLf
            End If
        Next j
    Next i

    If Len(doublons) > 0 Then
        MsgBox "Les lignes suivantes contiennent des doublons :" & vbCrLf & doublons
    Else
        MsgBox "Aucun doublon trouvé."
    End If

    Application.ScreenUpdating = True
End Sub