Mix the pudding, eggnog and milk in a bowl. Blend together for about 2 minutes then fold in the cool whip.
Spray a 9 x 13 pan with non-stick spray. Place a layer of whole graham crackers on the bottom, then top with 1/2 the pudding. (I had to break some graham crackers in half to fit in the small cracks).
Cover pudding with another layer of graham crackers, top with remaining pudding and another layer of whole graham crackers, then carefully spread the frosting on the graham crackers. (I microwave my frosting in the container for about 30 seconds and it will be a lot easier to spread on!)