Preheat An Outdoor Grill For High Heat And Lightly Oil Grate. In A Small Bowl, Mix Brown Sugar, Lemon Juice And Prepared Horseradish. Heat The Brown Sugar Mixture In The Microwave On High Heat 1 Minute, Or Until Warm. Score Both Sides Of Ham Slices. Place On The Prepared Grill. Baste Continuously With The Brown Sugar Mixture While Grilling. Grill 6 To 8 Minutes Per Side, Or To Desired Doneness.