Blueberry Graham Frozen Greek Yogurt

2% Low Fat Greek Plain Yogurt 3/4 cup granulated sugar 1 tbsp lemon juice 1 tbsp vodka (to keep the froyo from freezing too much in the freezer) 3/4 cup fresh or frozen blueberries 4 tbsp granulated sugar 1/2 tbsp lemon juice 5 graham crackers, crushed