Here's why you're not likely to see Adam Sandler and Cameron Diaz together in a movie any time soon: What studio could afford to pay both of them? According to the latest edition of ''Guinness World Records,'' published this week, Sandler is currently Hollywood's best-paid actor, and Diaz is filmdom's top-earning actress. Guinness calculates that Sandler pocketed $49.5 million in 2001, while Diaz took home $42.2 million. Sandler dethrones last year's highest-earning actor, Bruce Willis, though Willis had a much better year when he was on top; he collected $70 million in 2000. Similarly, Diaz takes the crown from Julia Roberts, whose 2000 earnings came to $21.2 million. Still, Willis and Roberts may be able to win their crowns back. Willis would have to be willing to make more pee-pee jokes. As for Roberts, maybe she just needs some new hair gel.