Preheat the oven according to the directions on the box.
Pour the dry cake mix into a bowl. Whisk in the cinnamon and nutmeg.
Now mix in the eggnog, vegetable oil, eggs, and rum or rum extract.
Pour the batter into a greased 9 by 13 inch pan and bake according to box instructions.
After removing the cake from the oven, poke holes in the top. Then pour the sweetened condensed milk over the cake, making sure to get some in each of the holes.
Refrigerate at least four hours. Before serving top with Cool Whip. Lightly dust with nutmeg or cinnamon.
I used Betty Crockers Super Moist White Cake Mix that calls for three eggs, 1 1/4 cups water, and 1/3 cup vegetable oil. I replaced the water with eggnog. You could use any white cake mix you like, just swapping out the water amount for eggnog.