Illustrator help! Damn this blob!

Hey guys! I’m fairly new here and don’t post often, but I love this website and these forums, they’re a great source of information and help! Anyways… I need help with illustrator, and I hope that someone here can help me.

I am trying to create a sort of a “highlight” or “shadow” effect on a blob type shape that I have drawn.

Here is the blob.

I then drew a rough shape around the blob where I want my highlight to be…

What I want to do, is intersect it or cut out the area of the shape that I wont be using for the highlight. I hope this makes sense… to create something like this… ( keep in mind, I did this final pic in photoshop, its very rough but I hope you get the idea. )

I tried using the divide tool in pathfinders, and then deleted the left over shapes. It SORT of worked, but my strokes were all messed up. what i pretty much wnt to do is instead of giving each newly cut out shape it’s own stroke, I want to put a single stroke over 2 shapes, which are DIFFERENT COLORS that I have recently devided. Problem is…is that I don’t know how and I’ve been confused as hell for a few hours. Add to shape area won’t do it because it will make everything the same color, which is something that I don’t want. I even tried grouping the two shapes, and then applying the stroke, but I yielded the same effect.

So please! Kirupa, pimp my vector!