Formula Controller for auto-leveling problem:

I'm a bit rusty and never understood formula controller in the deepest depths but always used it with its basic functions.
I discovered the "Case(switch,argument1,argument2)" operator and it's really cool.
How could I make a volume leveller out of it?
I have the formula Case(a>=b,argument1,argument2) whereas B is the target threshold where I want to apply volume limiting.
Say that B is 0.8, which is a fair target volume, how would I make anything above 0.8 be formulated in order to reduce the volume by the right amount?
My goal is to make a long-term leveller and a short-term noise reducer so to reduce heavy sounds but to raise voice volume.
And my goal is to have a stable amount of LUFS.
I would appreciate that someone help me do the maths.
The formula that works for me right now is this:
case(a>=b,a-b,b-a)+c whereas C is volume, B is target and A is input (peak controller) but it's not ideal and don't feel the dynamism I'm looking for.
Also, I'm connecting it to a gain button, but I could also use a compressor ratio button.
I need a very reactive but precise set of formulas.
Also, I'm using X Y Z controller for smotthing, and "Decay" for release.

What's your strategy to stabilize the perceived LUFS automatically?

I've been using Playlist Rider for a while but it's really CPU hungry so I'm trying to fiddle around with an alternative solution.