cellphone detector for incoming call

[arsal_uet]

i have been assigned a project by my really harsh professor by giving such a project so near to the exams. he has assign me to make a circuit that dettects the incoming call, but the problem is he has made a condition if two mobile in the reach are being called simultaneously then that dvice or the circuit should tell that either they are being called from the same bandwith or the difernt ones, that is are the being called by using the same mobile network or the different. i have seen the circuit here which just tellls us the incoming call from any network any i think, but me want ur help  how to make it for atleast two networks and how to make the ciruit sensitive to two seperate networks. and also how to show either using some leds or stuff like this.
thanks for ur suggestions.
http://electronics-lab.com/projects/misc/010/index.html
the source of the circuit given on this site is above.