Guymon's Easy Microwave Marshmallow Popcorn

2 bags of microwave popcorn
1/2 c. margarine or butter
1/4 tsp. baking soda
1/2 c. brown sugar
10-12 large marshmallows

Microwave margarine, brown sugar, and marshmallows on high for 1 1/2 minutes. Stir. Cook for 1 minutes more on high. Add baking soda. Stir and cook for 5 seconds. Stir and pour over popped corn.