Hi,
try out this option,
using Excel = Microsoft.Office.Interop.Excel;
Excel.ChartObjects xlCharts = (Excel.ChartObjects)excelSheet.ChartObjects(Type.Missing);
Excel.ChartObject myChart = (Excel.ChartObject)xlCharts.Add(10, 5, 300, 250);
Excel.Chart chartPage = myChart.Chart;
Excel.Range chartRange; = excelSheet.get_Range("A20", "B30");
chartPage.SetSourceData(chartRange, Type.Missing);
chartPage.ChartType = Excel.XlChartType.xlColumnClustered;
myChart.Chart.HasTitle = true;
chartPage.ChartTitle.Text = "Column Chart";
--Sowraaj