I could try to learn how to do this myself, but it seems a waste of time when I'm sure there's people here who know how to do this in a few minutes.  Here's hoping!

The idea is to use a program like AutoHotKey (other options are welcome) to provide an alternative way of closing dialog boxes in the game Gems of War, launched from Steam. Basically, the near thumb button on my mouse will go Back in browsers, and I want it to do the same in Gems of War.

Here's the technical detail (please ask if I've missed anything):
- Assign near mouse thumb button to generate Esc-key keystroke.
- Diablo III designates this mouse button as Mouse4.
- Only active while GemsOfWar.exe is running, and preferably only while in the foreground.

Thanks in advance!