Need help with a nurbs evaluator

I need to determine a set of points which lie on a surface (x,y,z coordinates for each point in the u and v directions) when given a knot
vector, control points and weights in NURBS format. I know that there are NURBS evaluators in openGL (glEvalCoord), similar to using a vertex, but I do not know how to obtain the coordinates for each point that it has generated from the evaluator. Any help that you could provide would be helpful. Thank you.