Creating a solid from two spline shapes

Since my knowledge of NURBs is poor, this is what I have done (or want to do) so far. I have a tricky CAM part that needs modelling. I have created the front and back shapes using a Line spline. The back is offsetted from the front by the distance I need. Now what I want is to use both faces and create a solid. Now the loft command does seem to want to do this (can only do Path and shape, not shape and shape), so I tried NURBS. I convert one spline to a NURBS, and attach both splines together. I try and use the CAP command to create a CAP surface, and then ULOFT, followed by a CAP. This however does not seem to work. The ULOFT works, but I get mixed results as I can onlt pick certain 'pieces' of the spline. I have no problems if I originally create a CV or point curve, then CAP. So my qwuestion is:-

Is there an easier way to get what I want with spline? Or do I have to use an original NURBS curve?

Please help.....thanks.