[PyMOL] Atoms selection: Residue depth

Dear PyMol users and authors,

I am working on writing a plug-in for pymol and
I have a question regarding the selection of atoms.

I would like to select through the interactive window
(shift+left-click) atoms which have a specific depth
from the solvent-accessible-surface.

To do so I thought to modify this selection system
in a way that the window created for the selection
has a maximum depth in the space.

Do you have any suggestion?

Thanks,

Giacomo Bastianelli
Ph.D student