I am trying to cut a smooth, continuous, curved track on a spherical surface (think of a metal ball ~ 4" diameter with a ball bearing race cut into it).  The 'Wrap' feature in 2008 does not support a spherical face to wrap a sketch onto.  I have been able to form basic tracks with reference planes, and then perform a swept cut on those sketches, but the end result is not the smooth curve I am looking for.

Can anyone provide a solution?