Mapping Multiple Buttons presses to a single input.

[Piecewise]

I'm playing Dissidia 012 right now and their habit of mapping very commonly used actions to R+some other button is giving me a wicked hand cramp. The easiest way I could think to remedy this is to just map these commands to the otherwise mostly unused trigger buttons (I don't need to speed things up that often and can do save states using the keyboard) while playing that game. However, I can't find any option to bind a multiple key command to a single key input.

Does this option exist? Can you bind, for instance, R+triangle to the right trigger?