RFID part tracking

I am new to arduino but am eager to learn as much as possible.

I am interested in creating a system that will track how long a passive RFID tag is within range of a reader and outputting the time to a spreadsheet. Can anyone provide some of the basic components this system will require?

-Arduino -RFID shield (similar to the RFIDuino) -passive tag

Any info at all would be very greatly appreciated!