POUR caramel sauce into 12-cup fluted tube pan sprayed with cooking spray. Blend evaporated milk, cream cheese, 4 eggs, vanilla and sugar in blender until smooth.
BEAT cake mix, water, oil and remaining eggs with mixer until blended. Add sour cream; mix well. Pour over caramel in tube pan; gently ladle flan mixture over cake batter. Cover pan with foil sprayed with cooking spray, sprayed-side down. Place in larger pan. Add enough water to larger pan to come halfway up side of tube pan.
BAKE 1-1/2 hours or until toothpick inserted near center comes out clean. Cool completely in pan on wire rack. Refrigerate 2 hours. Loosen dessert from side of pan; invert onto plate. Remove pan. Serve dessert topped with COOL WHIP.