Preheat oven to 350.
Gradually melt caramels and 1/2 Cup evaporated milk in microwave. I do it in 30 second increments stirring after each 30 seconds until melted.
Grease and flour 9 x 13 inch pan.
Combine cake mix, melted butter and 1/3 Cup of evaporated milk. Spread half of mixture in pan and bake at 350 for 8 minutes. Sprinkle chocolate chips over baked crust and pour carmel mixture over top. Crumble the rest of cake mixture over and bake for 18-20 minutes. Cool.
You can keep in refrigerator or room temperature.