Preheat the oven to 350 degrees and set the rack to the middle, or just above middle of the oven. Coat a 9 by 13 inch pan with non-stick spray. Mix the cake mix, evaporated milk, and margarine together until cake mix is moistened. Put 1/2 of the cake mixture evenly across the bottom of the 9 by 13 pan and bake for 10 minutes. Remove the pan from the oven allow it to cool for a few minutes. Sprinkle the chocolate chips over the baked cake and pour the caramel sauce in drizzles across the chocolate chips. Do not try to spread the caramel sauce. If the caramel sauce is too thick, warm it in the microwave or a pan of hot water to thin it out. Pat spoonfuls of the remaining cake dough into patties and place them across the top of the caramel, as island of cake. Bake an additional 15 minutes or until the cake is cooked.