PREPARE cake mix batter according to package directions using water, oil and eggs. Bake according to package directions in 13 x 9-inch baking pan. Cool on wire rack 5 minutes. Poke about 8 dozen holes in cake using round handle of wooden spoon.
MIX sweetened condensed milk and caramel topping. Reserve 1/2 cup mixture for topping. Pour remaining mixture evenly over warm cake. Cool completely.
STIR whipped topping and reserved caramel mixture in medium bowl until blended. Spread evenly over cake. Sprinkle with chopped candy. Chill until ready to serve.