In a large stockpot, bring water,& bouillon to a boil; this will be the final pot your soup is in. Add celery, carrots, onions, & pepper; cook for about 4 minutes or until tender.
Add macaroni, & bring back to a boil. Cover & boil 2 minutes. Remove from heat; let stand for 8-10 minutes til macaroni is tender.
Meanwhile, melt butter in a large enough sauce pot to be able to hold the milk amount. Add flour to the butter, stirring until smooth & begins to cook a little. Gradually add milk, stirring constantly using a whisk. It will begin to thicken. Cook & stir 2 minutes. Turn on low or off & add cheese; stir til melted. Add to undrained macaroni mixture.