need some help on a project.

Posted by argh
After some real deep googling i ve found nothing on my project.So i need some help.
I have that old Siemens sl45,good inet connection on my home PC, an Unlimited Mobile-to-Mobile plan and my p800 of course.I want to share the inet connection over the GSM network so i can have unlimited and free access to the inet with the p800.My old sl45 will be the trasmitter.But there is the problem.What software should i have, it must make the sl45 answer my calls and encapsulate the inet connection using the right protocol type and encapsulation.
10x in advance