ASA does not support PBR - not in the same sense as we support it on routers.
There was a plan to introduce in one of the future releases (AFAIR it's not going to be the upcoming 9.0 release). COntact your SE for details and/or building a business case to have this feature integrated.
There is a way to do poor man's PBR using NAT, but it's not a deployment I would recommend. You can divert all traffic on particular port out a certain interface (among others). If you dig in a bit you'll find examples - I believe there is also a supportforums document available by one of our colleagues in India.
M.
