Prepare and bake cake mix according to package directions for 2 - 9 inch layers. Cool cake completely.
With a long serrated knife, cut each layer in half horizontally to make 4 layers. set aside.
In a large bowl, mix the confectioners' sugar, sour cream, and coconut. Spread between layers, and on top, but not on the sides of cake. Place in large container with cover, or wrap in plastic, and place in refrigerator for four days before serving.
