In the tradition of cranking out useful plugins for Cinema 4D, the C4DZone releases Spline Extruder, which will allow you to take a polygon and extrude it against a spline in C4D.
Spline Extruder is a r13/r14 Cinema 4D plugin that combines the power of Sweep Nurbs modeling with the Box Modeling by extruding a polygonal selection using a spline path in real time
The Spline Extrude Plugin actually creates all the object you need based off of a polygon selection, simply adjust the newly created spline, and extrude your face against it. Really helpful for all kinds of modeling tasks.
One benefit of Spline Extruder, is that it is all in real time, meaning that you are able to create animations of the spline and its parameters and have the resulting extrusion follow suit.
To find out more about Spline Extruder for Cinema 4D check the page here.