Decrease Regeneration After Every Special Attack

I am having issues trying to decrease the value of either regen rate float or energy regen float for my character’s energy (or mana) every time the special attack is used. The goal is to have the value decrease further and further down, making it take longer to regenerate the energy for the cooldown I have in place. I have the screenshots of the special attack (Water Blast) and the energy regen. Any help would be awesome!