SelectSlope

I have selected a slope that I am using as mask for a SandLayer

Now, in this Selected slope I want to make a new selection, for a new DuneLayer.

What I wish for is a way to make the DuneLayer selection, within the SandLayer selection -10
like this

I am seting up the Sandlayer from a macro

I added a picture to visualize it

get the firrst select slope. create a new one, with the smaller slopes. use a combiner node set to subtract, and subtract the smaller one from the larger one to get the inbetween.

also your english is kinda balls, not sure if first language or not, so could you please post a picture of your node graph?