In article <ant231159313Pk=+ at mrc7acorn1.path.cam.ac.uk>, Mike Clark <mrc7 at cam.ac.uk> wrote: > It all depends how complex an answer you want! Or how simplex an answer you want! The underlying principle might be exquisitely simple. Jamie Home pages http://www.ndirect.co.uk/~greenprac/jamie/jamie%20main.htm Sent via Deja.com http://www.deja.com/ Before you buy.