Dynamically darkening a building, terrain, etc?

I'm wondering if it's possible to dynamically darken a certain part of a map. Lets say there's a house and you want it to all of a sudden make it look like one side has a shadow on it. I'm not talking adding a unit without a model, i'm saying really shade the whole map shebang: terrain, doodads, destructibles, unit's too if possible. Like some kind of filter that makes that part of the map look darker.

Is this possible? WIth image tricks maybe?

you can do a dark fog to darken the enviorment and change vetex color in animations to darken units in-game

I don't think fog would cut it, i want it to look like part of the map is in a shadow, without a fog effect needed.

You could make it all dark (read:night) and light up areas with that nifty light sqaure someone recently posted.

That's no good either...thanks though.