Help with modifying Total actor hit points

[SilentGreyFox]

I've created a set of armor and would like to apply an effect to it that would make the user loose a certain % of their maximum health while wearing it.

 

Ex. Actor has 800/800 hp. When the armor is equipped, this gets reduced to 400/400 hp.

 

It's quite easy to reduce hp by a certain value (ie actor has 400/800 hp once equipped), however I haven't been able to figure out how to change the maximum value.