getting range values out of evaluators

I am using glMap to calculate cubic Bezier curves.
I would like to do something similar to glEvalMesh,
or glEvalCoords, in that I can pass a function a
domain value – but I would like the range value
returned. Those two functions just graph the
returned coordinates; I would like to have them for
further calculations. glGetMap just seems to return
the control points and other data I already have.
Any suggestions?