Preheat oven to 350 degrees F. Spray a 12-cup bundt pan with flour-added cooking spray or grease the pan with shortening and dust with flour.
Pour the caramel topping into the greased and floured Bundt pan.
Prepare cake mix according to package directions. Pour the cake batter into the cake pan over the caramel topping.
Make the flan. Pour condensed, evaporated and fresh milks into a blender. Add softened cream cheese, vanilla and eggs and blend until smooth. Pour the flan mixture very slowly over the cake batter.
Spray a sheet of aluminum foil with cooking spray (or just use nonstick foil) and cover the pan TIGHTLY with the foil. Covering tightly is very important. Set the Bundt pan into a large pan (such as a roasting pan) and set on the oven rack.
Carefully pour hot water into the larger pan to a depth of 2 inches (The Bundt pan will be sitting in 2 inches of water). Bake for two hours.
After two hours, remove cake from water and allow to cool for 15 minutes. Peel off the aluminum foil. Invert cake onto a large plate with rim. The caramel topping should flow down the sides. Cool completely then refrigerate.