A BSpline over a surface

[Aquileo]

I need to make a B-Spline over a surface. The program is CAD.

There are a shape and the user select various controls points, and with this points I must do a bspline over the shape's surface.

How can I do?

Thank you very much!
Josemi.

[AdrianD]

http://www.google.de/search?q=B-splines&ie=UTF-8&oe=UTF-8&hl=de&btnG=Google+Suche&meta=

[Aquileo]

There are over 24000 results. I don't have time to read all.

Please, I must do lines over a object in 3-dimensions, but the line should be interpolated with B-Spline.

Thank you very much for all.
Josemi