fintab = Sheets("Data").Cells(Rows.Count, 1).End(xlUp).Row
Sheets("Graf").ChartObjects("Graphique 1").Activate
ActiveChart.Axes(xlValue).Select
'série "valeur col2
ActiveChart.SeriesCollection(2).Values = Sheets("Data").Range(Cells(2, 2), Cells(fintab, 2))
ActiveChart.SeriesCollection(2).XValues = Sheets("Data").Range(Cells(2, 1), Cells(fintab, 1))