Cook macaroni according to package directions, omitting salt and fat. Drain and set aside.

Melt margarine in a saucepan over medium heat; add flour, and cook 1 minute, stirring constantly with a wire whisk. Gradually add milk, stirring constantly. Bring to a boil; cook 1 minute. Remove from heat; stir in dry mustard and next 3 ingredients. Add cheeses; stir until melted.

Combine cheese sauce and macaroni in a bowl; stir well. Yield: 6 servings (serving size: 3/4 cup).