Charts in C# 2010

Question

Hi...

I have created a spline chart.I added 5 points and drew the graph.But i neeed to mark some points on the plotted graph.how it is possible.When i tried to add these points and plotted the graph,the graph shape changed.Actually the graph's shape is predetermined,I only need to mark some specified points on it.how it is possible.

Plz help me...
Thanks in advance....