From our "Why would you keep THAT a secret?" files: For the past two weeks, Walt Disney Productions has declined to report grosses on "Benji the Hunted," which was playing exclusively in Dallas' North Glenn Theater (it opens here and in New York today). Wasn't "Benji" barking up enough tickets? On the contrary, the theater sold a hearty $21,500 worth of tickets on opening weekend and last weekend that figure jumped to $31,000, hardly dog food. "I just think it was because it was the only engagement nationwide," a Disney spokeswoman said. "We kicked it off there because Dallas is (director) Joe Camp's hometown."