Thanks for the brain melting question. ok... this is a pain but here is the work flow... you need to create a solid matte that is just want you want to show... AKA the gray area... then select the top group of your logo, and copy that new solid matte into that group as an "opacity mask". look in the transparency pallet. please note how your layers pallet changes... this is because you have drilled down into the groups opacity. to get back click on the left preview thumbnail in the transparency window.