Prepare and bake cake according to package directions in 2 8-inch or 9-inch round pans.
Once cool enough to handle, remove from pans and let cool completely.
After the cake is completely cool, cut each cake in half so that you now have 4 layers.
Blend cream cheese until soft; add sugar and continue to blend until sugar is dissolved. Fold in whipped topping. Assemble cake in layers. Cake, cream cheese mixture, blueberries and repeat with remaining three layers.
NOTE: Cake is best after being refrigerated for several hours. Also, try using chocolate cake with cherry pie filling.
VARIATION: Put first 5 ingredients in sauce pan. Mix corn starch with small amount of water. Blend into sauce pan and bring to a boil over medium heat. Let cool and assemble as above.