I've just bought a Linx 7 tablet which runs full windows 8.1 (surprisingly well) I will be using it as a normal tablet but I've also started setting it up with all the usual emulators on it with an Emulation Station frontend so I can just press the icon to get to the main menu with all the systems listed. I'm controlling it with an Xbox 360 controller.

Now my problem is getting back to the front end's menu as on most emulators you would press ESC to either exit or get to the emulator menu, but with not having a keyboard attached this is impossible.

So my question is how can I map a combination of buttons on the controller to for instance the ESC key? I'd like to have combos of say all 4 shoulder buttons as some emus such as PSX will use all the buttons on the controller as standard. I've seen things like Xpadder but that seems to more like mapping keyboard keys to one controller button but not the other way around?