Inbound call filtering?

I want to know how to make inbound call filtering? i will explain what i need to do.
When i take my cell phone with this number 888-888-8888 and call my asterisk PBX, i want asterisk to answer imediately, and play a dial tone and wait for a number to be dialed when the number is dialed like 1-888-999-9999, it take my IP line ans route the call, this way i can put my asterisk number into my free friend plan, i just have to call at my home always a free call and use my ip line to make every call, can someone give me some hints on doing this?? thanx a lot!

the things you will want to look at are
and disa

goodluck and be careful with disa if you dont have a password set it could be bad.