Frantic athletes who wantto run in the centennial race are scrambling through a black market obstacle course to land one of the 38,500 official entry numbers. The $50 numbers are going for as high as $500.

"We've had people calling up looking to get a number," said Charlie Rodgers, manager of the Bill Rodgers Running Center at Quincy Market. "They're saying, `Shall I go to the airport? Maybe there's someone coming into town. Or should I go to the Runner's Expo and poke around for somebody who's not going to run for some reason?' '