Heat oven to 350 F. Grease and flour 9 x 13 inch pan. Prepare cake mix as directed on package; pour into prepared pan. After 10 minutes of baking, sprinkle with chocolate chips. Continue baking until cake is done. While cake is still hot, poke holes in it with handle of wooden spoon. Pour sweetened condensed milk over cake; let cool. Top with caramel sauce, then whipped topping. Sprinkle with candy bars.