Hmm, that's pretty much the code i ended up with after I made the changes. I think I may have forgotten to update the vertex or index buffer though. Maybe that's why it wasn't showing up right.

Don't forget to update the primitive count parameter on the draw call, it's a very common mistake when it is hardcoded as in the example, it should be determined in function of the primitive type automatically, in TriangleList the number is NIndex/3, in triangle strip its NIndex-2