In a large bowl, using a mixer, combine all frosting ingredients and mix until smooth. If frosting seems thick, add additional water by teaspoonfuls until creamy and spreadable.
Spread top of cake with frosting and smooth evenly. Divide into 12 sections: 3 sections on the 9-iuch-end and 4 sections on the 13-inch-end. Here is a picture of how it will look:
B P C PP C B PC B P CB= Blueberry Pie FillingC= Cherry Pie FillingP= Pineapple Pie Filling Using a pastry bag with a star tip, pipe frosting along the dividing lines both east to west and north to south; fill each square carefully with designated pie filling. Refrigerate until ready to serve. Makes 12 servings. Enjoy!
Note: Cool Whip may be used instead of frosting, but the cake MUST be refrigerated before, and any leftovers should also be chilled.