Split brep with surface and show only what is above it

Hello all,

I have a small and probably simple thing to solve but I’m struggling a bit.
I have split a box using a surface and I want to see just what’s above the surface.
I have tried to solve that but no luck, would anyone have an idea how to do that?

List what’s above.3dm (280.5 KB)
List whats above.gh (3.0 KB)

use dispatch or explode tree

Thank you!