I think you can try it with "Functionplotter", which costs about 56.- DM
It only draws functions in 2- and 3- dimensions, but it can find zero-points of functions and it can solve differntiations and integrations, which can be automatically generated by the programm from your original function.
To get it, try calling the german main distributor : GMA in Hamburg.
Their number is 040/2512416 or 040/2512417, remember to add the international telephone code from England to Germany, this will be 01049, and then leaving the first zero blank.