Hi! have you put the TCP settings in the BB? It also depends on your provider. For exanple, I know a connection through CPW-O2 UK tends to block the use of BB as a modem. But if you were with O2 UK Direct then it wikk work. Also some providers will not cover the data usage through this means under this BB data plan. I am not aware of any software that will allow the function that you are asking.
Alternatively, you can play around with the TCP settings. sometimes using wap settings works coz that may get included in your data plan.
Check this link. Maybe of some help...Item code no 14 http://www.chumedh.com/bbwiki/tiki-wiki_rankings.php