you're gonna need some slack in the chain in order to do this (the kind of slack that comes from derailleurs, but i'm sure something can be worked out...), but finish line makes a really cool chain cleaner. clips on to the chain, fills with degreaser, and then you pedal through it. it really, really thoroughly removes gunk and ol lube. wait till the degreaser dries, then relube! i hear rad things about rock and roll gold lubricant.

the mechanics in the shop i work in use the chain cleaner and swear by it.