Buliding transparency mapping

[Heydari_cg]

I am an architect, and are trying to render a scene that I've made.... I have many buildings in my landscape-scene, and all of the bulidings in my scene have their own texturemapping (my bulidings are drawen as boxes with a texturemap, to show the buliding material, and the windows). I really dont have the time to draw all the details in my buildings as my scene is very large, and want to know if there is a way that I have brick material, and glass material in one material and use my alpha channel to define the windows?

Please help me my deadline is around the corner