it would be great to see what you come up with ..
again.. I never tried it but I was also thinking that if you could monitor and control the screw turn rate (eg cheap/easy micro controller like picaxe) you could (maybe) keep it accurate for longer.. depends how keen you are.. if you know V=IR (bout my limit of electronics) and some basic programming skills the picaxe is a very cheap and easy micro-controller to play with..
Please let us know if you want more info.. (I might start a new thread.. as my ramblings are getting a little of the topic
)
rgds
Jason