Mix together cake mix, margarine, and 1/3 cup evaporated milk and spread half of the batter in the bottom of a 9-x12-inch greased pan. Bake at 350 degrees for 6 minutes. Microwave caramels and remaining 1/3 cup evaporated milk on high for 2 minutes. Stir and microwave for 2 minutes more; stir. Spread over baked batter. Sprinkle nuts and chocolate chips over caramels and dot with remaining batter. Bake at 350 degrees for 20–22 minutes.