A game of handball is the setting for a Miller Genuine Draft :30 that broke yesterday on the West Coast during NBA broadcasts. Miller Brewing Co. will take the spot national today on cable. Targeting AfricanAmericans and Hispanics, the ad from Bates USA, New York, unfolds in an urban blacktop backdrop, to a hip-hop sound track. Two young men play handball against an enormous mural featuring MGD's new packaging. The ball seems to punch holes in the can, from which beer sprays out. The tagline: "Stay cool."