How would I add a new mechanic?

I'm trying to add a new mechanic called a "Combat Reaction". It comes out of the Trailblazer system and basically is a class of actions that players can take at any time during a combat under certain conditions. Attacks of Opportunity fall into the mechanic (as does "aid another", etc.)

The system limits the number of Combat Reactions based on BAB and a couple of Feats (Combat Reflexes, primarily.) I'd like to keep track of that in HL, but at the least I'd like a spot to store the number and track it's use every round.

Any suggestions how to do this? I thought about using the Counter in the Adjustments tab, but would like a way to build it in. But I'm guessing I'd need access to the Character Sheet to actually add it, right?

Oh, and almost all of the Trailbalzer rule-set is Open Content.

A tracker (shows up on the in-play tab in the tracked resources section) component exists, and will eventually be added to the editor. Once they're added, all the trackers will show up on the character sheet (with the ability to suppress that display if desired). Place a vote in the poll for the magic items - I'll probably add the trackers while fixing the tracker components of magic items.