Range cells = worksheet.Range["AR39", "BC64"];
Tools.Chart chart = worksheet.Controls.AddChart(cells, "Graph");
chart.ChartType = XlChartType.xlBarStacked;
Range group1 = worksheet.Range["$AW$8:$BA$37,$BC$8:$BC$37"];
chart.SetSourceData(group1);
Axis axis = (Axis)chart.Axes(
Excel.XlAxisType.xlCategory,
Excel.XlAxisGroup.xlPrimary);
axis.ReversePlotOrder = true;