There was some discussion a little while back about some precision control
of air or hydraulic pistons - I don't remember which - anyway, this valve
that I ran across is directly applicable - very cool valve (detailed
description in the listing, I won't take up space here)

here's the link
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7542065234

--
Bill



also check out http://www.wbnoble.com