New training tool for coaches and players?

I read some were that if you have the Madden 2003 game you are able to change the plays Off. & Def. to your own. Is this true and how do you do it? Would this be a great tool for your players and yourself to try out something new. And see how it goes against the different. I thought this was a great Ideal does anyone else?

Please Help

Thanks alot.