Allotment of 1 mb limit per person entering with IP address.

I have installed ubuntu 12.04 lts in my laptop. I opened 1 port from my O.S. I have an internet connection with [login to view URL] which is 110 mb/day. I wish to allot 1 mb limit per a person entering via port into my O.S(needless to say from [login to view URL] IP address). Facility to change 1 mb limit should be allowed in the source code by me should be provided. After 90% of the limit is used, facility to extend the limit be provided in the source code itself. i.e., it should ask me "do you wish to extend the limit" with yes/no options, if yes is clicked how much should be asked and after entry it should the limit should be extended. I need software to be given to me in C or C++ with compilation procedure and execution procedure.