Trainer type programs

Well, what I want to do is make a trainer type program, like the one for Dune 2000, that can give you unlimited money, instant building, etc. Trainers allow you to turn on and off certain qualities or enhancements that were not included in the original game. This could be Unlimited Lives, Unlimited Money, Invulnerability, etc. The trainer alters the original memory locations to allow you to "Cheat" where you wouldn't be able to do so without it. Most of the time in order for the trainer to make these adjustments the game and the trainer need to be running simultaneously. So it may be necessary for you to start the game then press ALT-TAB to minimize the game to allow you to start the trainer and activate it's cheats, then ALT-TAB back to the game. I am wanting to know if there are any tutorials about how to do this, or if anyone here can give me info.