I may be wrong, but last time I checked (for Warrior's double-charge talent at least) these effects put a buff on the player. You could set up some trigger combination for it - if you have the buff, you've got one charge left. If the spell is on cooldown and you have no buff, you've got no charges left, and if the spell is off cooldown and you don't have the buff then you've got two charges.
I'll play around tonight and see what I can do, maybe implement it as a Charges source/trigger combo. Thanks for the idea
