Preheat oven to 350°F. Coat a 9" x 13" cake pan with cooking spray. Set aside 1 cup of yellow cake mix. Mix margarine and one egg and add to remaining cake mix. Slightly press dry mixture into bottom of pan to form a crust. Combine pumpkin pie mix, two remaining eggs, and evaporated skim milk. Pour over prepared bottom crust. Mix the 1/8 cup reserved cake mix, sugar and cinnamon and sprinkle over pumpkin filling. Bake 45 to 55 minutes, or until filling is set. Makes 24 servings.