Postprocessmaterial , acess of Tonemapper?

Hey is there any way to acess the Tonemapper or ColorGrading Variables in an PPMaterial ?

like in the DOCS IS :

Scalar parameter:

Engine.FilmSaturation
Engine.FilmContrast

In order to get the parameters you need to create a material instance from the post process material.

but i didnt get any way to get acess of it .