Also, in the first program, could you possibly explain how these 2 lines work: inde:=2*Sample(x,1)[1]-1: S[i]:= S[i-a]+`if`(inde=1, inde*iv, inde*dv); I understand the rest, thanks.

Thank you that's brilliant. I'm yet to test it. But thanks for you help. Sorry to bother you further, but if I later wanted to adapt this to a situation where there were more than just the two possibilities (increase/decrease), to maybe increase, decrease, stay the same, or increase, increase by 2 times the increment, decrease for example. Where the total probabilities of these things has to add up to one. Would that be possible? Thanks