Preheat oven to 180 degrees C. Grease a 23cm cake tin.
In a heavy saucepan, combine caramels and 1/3 cup of evaporated milk. Cook over low heat stirring constantly until smooth then set aside.
In a large bowl stir together the cake mix, melted butter and 1/3 cup of evaporated milk by hand until dough holds together. Press half of the dough into the prepared pan, then reserve the rest.
Bake for 10 minutes in the preheated oven. Remove from the oven and sprinkle the chocolate chips over the crust then pour the caramel mixture evenly over the chips. Crumble the remaining dough over the caramel layer and return to the oven.
Bake for an additional 15 to 18 minutes in the preheated oven. Cool in refrigerator to set the caramel before cutting into bars.