Check out Sheldon's Alternate Cable Routings section, as it's what you want:
http://sheldonbrown.com/derailer-adjustment.html
Excerpt:
Shimano originally publicized an alternate cable routing which placed the cable slightly closer to the pivot, making the derailer move slightly
farther for each click. This adaptation makes newer Shimano derailers work with
older Dura-Ace shifters, but it is also useful when you want to use a 9-speed cassette with 10 speed shifters, or 8-speed cassette with 9-speed shifters, or a 7-speed cluster with 8-speed shifters.