How to create Balance/Contrast parameters?

Hello everyone!

There are two parameters in Grunge nodes: Balance and Contrast. I would like to create the same parameters for my own graph, so I can use custom grunge maps and then export an SBSAR file to Substance Painter. I know I should use a Levels node and create custom functions for "Level In Low" and "Level In High," but I still can't figure out how to create a proper function. I tried asking ChatGPT, but its functions do not work as well as I want them to