Combine sugar and water in medium saucepan. Heat, stirring, until sugar dissolves, then boil 5 minutes. Cool. Force berries through food mill or blend in blender or food processor. Strain to remove seeds, if desired. Blend strawberry puree and lemon and orange juices into syrup. Pour into freezer trays and freeze. Remove from freezer 20 minutes before serving. Turn into bowl and stir with wooden spoon until smooth. To make an especially attractive dessert, present scoops of ice in cantaloupe or honeydew melon halves. Makes 8 to dozen servings