Is there an application for this?

I have to make a work schedule for everybody at my, um, work. I have the times everybody is available.

Is there an application where I can set up a time grid (like Monday-Friday across the top, 8:00am-10:00pm down the side) and make a layer for each person, showing the times each are available, so that I can see what times multiple people are available (where layers overlap), and what times no one is?

Like Excel, but with layers?

If I sound crazy and nothing exists, I guess I can write it myself, but I'm not good with the Cocoa framework so I'd rather not.