On the heels of Air Bud's modest success Disney's canine-powered comedy has grossed $11.4 million in two weeks the film's producers, Keystone Entertainment, will make a football-themed sequel, Air Bud: Golden Receiver. Remarkable news, considering that shortly after Air Bud wrapped, Buddy, the film's 9-year-old golden retriever star, had his right hind leg amputated following the discovery of a cancerous knee joint. ''We even have a treatment for [a third film], Buddy in the World Cup,'' says an enthusiastic Robert Vince, president of Keystone. The filmmakers seem undaunted by Buddy's postoperative condition and insist that although canine doubles will be employed for many scenes, Buddy, who has recovered fully from his ordeal, will play a major role in the film. ''He is still able to catch a regulation football in his mouth,'' says owner and trainer Kevin DiCicco. ''And although he's a little more limited, he can still shoot baskets into a 7-foot hoop.'' As far as Buddy's handlers are concerned, his disability shouldn't limit how many more dog years Buddy has left in Hollywood. ''You couldn't keep that dog out of show business,'' says the pooch's publicist, Mike Baumohl. ''He loves the crowds. He loves doing what he does. He thinks it's better than sex and eating.''