A simple way of doing it would be to first create a triangulated representation of your surface (e.g. based on Delaunay tessellation or if derived from a quadrilateral mesh see my file submission mesh2tri). If you have a list of faces (triangles) and vertices then you can export this to STL format (which is basically a file containing your triangle list) which can be imported into CAD software. I think there are various files submitted to the file exchange concerning exporting of STL files.
Kevin
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