I am accessing excel through .NET C#..

I have two data series in a chart(XYScatterLines)..And I want to vary color
by point
of one series ...Infact I am not able to do that directly in excel manually...

Please help me out....

I even Tried following code..

grp = (ChartGroup)newChartObject.Chart.ChartGroups(1);
grp.VaryByCategories = true;