Combine cake mix, oil, melted butter, water and half of the condensed milk until well blended. Pour half of the mixture into a greased 9 x 13 pan. Bake at 180ºC for 30 minutes. In double boiler, melt caramels with remaining half of condensed milk. (takes about 15-20 minutes). Pour over warm cake layer. Sprinkle with chopped pecans. Pour remaining batter on top. Bake 30 minutes or until top springs back. FROSTING: Bring butter, evaporated milk and cocoa to a boil. Add confectioners' sugar and vanilla. Beat until smooth. Spread on cake. OPTIONAL: Decorate cake with whole pecans. ----