Cook macaroni about 3 minute less than the package directions.
While the macaroni is cooking:.
Grate about 2 ounce each of colby, monterey jack and half of the cheddar. Cut rest of the blocks into medium cubes. Slice the Velveeta. Set aside 1/2 cup of grated cheese to mix with bread crumbs.
Drain macaroni. Put butter, milk, grated cheese, celery salt, onion powder, salt, pepper, vegetable seasoning, cheese sauce in can and sliced Velveeta in a large saucepan.
Heat on low heat until cheeses are creamy. Put hot macaroni in large bowl. Add sauce, mix well. Add beaten eggs and mix well. Add cheese cubes. The cheese cubes will not melt completely. Add more milk if needed. Mix thorougly. Adjust seasoning if necessary.
Pour into large baking dish. Mix remaining grated cheese and 1/3 cup bread crumbs together. Sprinkle on top of mac and cheese. Drizzle 2 tablespoons melted butter on top of grated cheese and bread crumbs.
Bake at 350 for 35 to 45 minutes. Put under broiler to lightly brown the bread crumbs on top. Let set 15 minutes before serving.