Hmm, Well ive never rly Heard of that before, Perhaps u are thinking of Editing The amount of EXP u get In a Game.
Seeing as u are on Xbox, U wud have to connect ur Xbox to ur Computer, Somehow get into the Files, Acccess ur MW2 File, And look up the Player Files, Edit the File and find the Exp Section, and edit it from 100 to 9999999.