Bring to a boil in 1 quart Pyrex - sugar, margarine, and syrup. Then cook for 2 min on full power. Remove from Microwave and add baking soda. Stir well. Spray Pam on inside of a large brown grocery sack. Pour popped corn into it. Pour syrup over the corn, fold down the top of the sack. Inset into microwave and cook on full power for 1 ½ min. Shake well. Cook 1 ½ min, shake, cook ½ min., shake. Open bag and allow cooling. Shake.