[PyroPhin]

it definetly is possible, i dont know how accurate it is.. but our team has done it in the past.

it basically consists of attaching another solenoid to the exausts of the one controlling the piston you want released. you energize the primary one to either bring the piston in or out, then momentarrily tigger the one attached to the exaust untill you find your desired length.

as for the actual indexing... the only suggestion i can think of is put a pot on whatever your moving with the thing and get a reading off of that, or mark the actual arm (like this | | | )of the piston and use an optical sensor to record the ammount of lines that have passed. that would give you a somewhat accurate reading..

~Pyro