In a 5 quart Dutch oven, cook macaroni noodles as directed on the box. Drain. Pour into a large bowl. In a separate bowl, open the packages of the macaroni and cheese and pour into the bowl. Beat eggs, milk, salt, pepper, and margarine into the mixture. Pour noodles into a casserole dish. Pour custard over noodles. Bake for thirty minutes in a 350 degree oven. Cut blocks of Velveeta cheese out and place over the top of the casserole. Bake for five more minutes.