You don't need to be Eric Heiden or even Dick Button to take on this month's Challenge. If you can Rollerblade, you're almost ready to try marathon ice-skating. Later this winter, events from 5 kilometers up to 200 kilometers (3.1 miles to 124 miles) will be held in the storybook-pretty Austrian Alps, and at five other spectacular locations in Sweden, Canada, Vermont, and Utah. Although the longer distances may seem imposing, we'll show you how to maneuver on ice better than a Zamboni. Elite skaters slice through a 200-K at 23 mph. But don't try that your first time out. Instead, be content to enjoy the rhythm of the glide and the awe of cutting across a frozen lake with hundreds of other skaters.