"challenge complete" trigger

so is it possible to complete operation during in game by press a button in a "hand-made" program? I mean that for example i need 500 kills with the grip, during the game, i just press a button in a trainer and voila - i see the messsage "challenge complete"

where i can find or maybe someone can give an example of program to read/write values of process's memory during the game?
p.s. about answer like "google will help you" i've tried some guides from it - don't find correctly working one yet