LOCATOR

We are going to build a locator device using infrared..for example: there is an infrared receiver inside the room # 3, and infrared transmitter attached to an ID..when he/she enters the room, the IR transmitter will transmit data into the IR receiver and it should be display the room # into the 7 - segment display..The problem is, how can we build an IR transmitter using a 40KHz IR receiver, and how it will be display the exact room # into the 7 -segment display using pic16f84a.Please help me.. Thanks in advance..