Preheat oven to 350. Grease 9 x 13 pan. Mix pumpkin, condensed milk and eggs and pour into pan. Sprinkle top of pumpkin mixture w/ dry cake mix and chopped nuts. Drizzle melted butter over top of cake mix. Bake 350 for 1 hour. Cool and cut into squares. Serve w/ dollop of Cool Whip. ENJOY!!!!