1 (18 1/2 oz.) pkg. butter flavored cake mix
8 oz. carton sour cream
1 1/2 c. Cool Whip
2 c. sugar
12 oz. pkg. coconut

Prepare cake according to package directions, making 2 layers. Split both layers horizontally after they have cooled. Blend together sugar, sour cream and coconut and chill. Spread all but 1 cup of sour cream mixture between the 4 layers. Blend the remaining cup of mixture with Cool Whip and spread on the top and sides of cake. Seal in an air tight container and refrigerate 3 days before serving.