Try the pd software Kinsim, ftp from wuarchive.wustl.edu, in public/kinsim.
Also the Bioquest project have a Kinetics simulation for the Mac, Rate It!
Fergus Doherty,
dept. Biochemistry,
University Medical School,
Queen's Medical Centre,
Nottingham NG7 2UH
Tel: 602 709366 FAX 602 422225 Internet: mbxfd at unicorn.nott.ac.uk