Blueberry Refrigerator Cake
["3 layers favorite yellow cake mix", "1 (8 or 9 oz.) carton frozen whipped topping, thawed", "1 (8 oz.) carton commercial sour cream or 1 (8 oz.) pkg. cream cheese", "1 c. powdered sugar", "1 tsp. vanilla", "1 (21 oz.) can blueberry pie filling"]
["Mix topping, sour cream or cream cheese, sugar and vanilla. Spread on each cake layer.", "Spoon blueberry pie filling between cake layers and on top layer.", "Place in cake saver and refrigerate until all is served."]
["frozen whipped topping", "sour cream", "powdered sugar", "vanilla", "blueberry pie filling"]