Shadow between NSViews

I am currently working on an app which displays a subview with a progress control when it's doing some work. The subview appears from the top of the window using animation, and hides back when the operation is finished.

It looks like this (sorry, can't post images yet): screenshot: view without shadow

what i would like, is to make a drop shadow between those views, to make it looks like if the progress windows is just over the list view, not just above i开发者_StackOverflowt. It's difficult to explain. It would be something like this:

screenshot: progress view with drop shadow

I really don't know how could i get that effect using cocoa.

best regards

Use -[NSView setShadow:]. See the NSView docs for full info.