How To Make Curved Surfaces

Hey Mugen, I got my NURBS surface the way that I want it to in terms of shape. Do you know how I can customize the edges? Currently it seems like it is displaying a curved surface that is basically a curved rectangle. How an I terminate the edge where I would like it to? Please see how it is displaying as is:


image
It should be displaying as is. Basically if shape is terminated at the correct edges, the shape would be correct:
![image|391x330]