Hi rob and Aractus, thanks for your replies the other day. They were both very interesting. Probability is one of my favourite subjects and I'm never happier than when I'm making little board or computer games based on it, but that was back when I had a lot of time on my hands. Now I don't so as much as I could see myself getting obsessed with this, and whiling away the hours trying to figure it out, I just don't have the time... so just saying it looks fun but I'm gonna have to leave you to it. Have fun 
