Dissolve gelatin in boiling water. Spoon in ice cream. Stir until melted and smooth. Chill until slightly thickened, about 10 minutes. Pour into crust. Chill until firm, about 2 hours. Melt margarine with chocolate; cool. Spread over pie. With knife, lightly score pie into serving-size pieces. Chill until chocolate mixture hardens. Serve with whipped topping and berries.