Thanks for the info, but not sure I can use that, so thought I better explain a bit more what I am looking for....

I want to draw a surface where the surface will pass through every point and interpolate between the points to give a smooth curve/surface. For 2D I use cubic splines which work very well. I have a 3D polynomial least squares fit routine but it is not good at any points outside the dataset and also at higher powers the surface gets "wobbly". What I intended to do was run a series of cubic splines along the X and Z planes which should work but would be cumbersome, so I was hoping that someone may already have a routine for taking the dataset and produce a set of equations to generate the qaudrilaterals for my OpenGL routine for plotting. This plotting routine works well for the 3D polynomial data so I only need the routine to generate the points. See the attached picture for the current plotting routine.

Hope that makes sense, would appreciate any help, thanks in advance.