Make chocolate cake according to package directions, adjusting for altitude, if necessary. Bake and cool on rack. Slice each layer horizontally through center to make 4 thin layers. Spread about 1/2 cup whipped topping over bottom layer; top with small amount of pie filling. Place on next layer and repeat topping and filling. Finish last layer with whipped topping piled up around edge and with filling deeper in center. Chill.