Masking tracking areas

how can i track an area while having another object in front of it? how do i tell a roto that it’s a mask for the tracking of another roto? i’ve seen it done in monet!

it worked, thank you

—Quote (Originally by adrian cruceru)—
how can i track an area while having another object in front of it? how do i tell a roto that it’s a mask for the tracking of another roto? i’ve seen it done in monet!
—End Quote—

Foreground layers subtract from Back ground layers.

i.e. on a setup with

Layer 3
Layer 2
Layer 1

Layer 3 will be masked out on Layers 2 & 1
Layer 2 will be masked out on Layer 1