I'm not sure if this will work for Facebook. WiFix by Aerize works with some programs and might do what you're looking for. It works for some things like Google Maps Mobile, Blackberry Maps, etc. (which require a data plan)
I haven't tested it myself but I don't believe that it will work since one of the limitations in the program is that it doesn't work with HTTPS/SSL connections and I believe that Facebook uses this.
__________________ Rogers Wireless (BIS only data plan)
: Rogers Blackberry Q10 (white) My Tech Blog