Assembly Envelopes controlling State

Hi

It says in the help menu that an Assembly envelope can be used to indirectly control suppress/resolve states - does anyone know how to do this?

I have an assembly where I wish to suppress certain parts when the assembly envelope crosses/contains those parts, but then unsuppresses those parts when the assembly envelope no longer crosses/contains those parts. It's sort of like a floating "mask"

To make it more interesting, those parts are parts within a linear pattern.

Thx

KEN

SolidworksAssemblies