I actually use CapsLock as a hotkey toggle. When it's off, I'm broadcasting as normal, when it's on, I'm broadcasting all keys to all windows for emotes and reloads and the like. I've also used it to toggle between AOE DPS and ST DPS, both to swap the keys/macros it's calling and to have mouse broadcasting enabled for dropping Targeted AOE. It's nice to have the CapsLock light as a visual indication.

I couldn't tell you how to do it with ISBoxer, but since I can do it with HKN, I'd guess ISBoxer can do it too.