If you mean a macro controller, then yes it can be done, several ways. Viking did this on the 360 controller, and a friend of mine and I made a fully remappable 360 controller with a bit of 'hard coded' Macro support as well. Neither of those projects were cheap to do in time, money or effort wise, or built in a day. Without you either learning a bit of programming and/or hardware level designing, or forking out the money for someone to do it for you, as a controller like that isn't the norm, you'll probably never see one.
Using something like the Cronus would be the easiest way to go about it, as well as not require you to touch the insides of the controller in any way. Any other method will mean opening the controller up and doing quite a bit of soldering as well as some hardware design and then coding for a PIC, Arduino etc, etc. and then maybe even some PC programming, depending on what kind of interface you want to have with the thing.