how to find points on subsurfed surface?

I am rather new to python scripting and I would like to write a script that calculates a tangent between to subsurfed objects. Now I don´t know how to deal with subsurf. If one of my objects is a cone and I would like to draw a tangent from its tip to some other object, I would use the tip vertice. But if I add a subsurf modifier, the tip of the cone gets rounded and gets an offset to the original vertex. How can I find a point on the subsurfed surface? Is there a sample script of this subject that I could study?
Any help greatly appreciated!

Look up the python NMesh api docs. - linked from my homepage,
Blender.NMesh.GetRawFromObject(on.name)

Thanks, I will look into that.