Put popped corn in brown grocery bag.
Put brown sugar, margarine, salt and syrup in glass or plastic bowl. Melt on high in microwave for 2 minutes. Take out, stir, and boil for 3 minutes, stirring after each minute.
Add soda and vanilla and beat. Pour over corn in grocery bag. Shake and close bag.
Put in microwave 1 minute. Shake.
Put in 1 minute. Shake.
Put in 1/2 minute. Shake.
Put in 1/2 minute. Shake.
Take out and put on waxed paper to cool.