Cook macaroni according to package directions. Meanwhile, in a large nonstick skillet, cook the turkey, celery and carrot over medium heat until meat is no longer pink and vegetables are tender; drain. Add the tomatoes, tomato paste, water and sloppy joe mix. Bring to a boil. Reduce heat; cover and simmer for 10 minutes, stirring occasionally.
Drain macaroni; set aside. In a large saucepan, saute onion in butter until tender. Stir in the flour, mustard, salt and pepper until smooth. Gradually add milk and Worcestershire sauce. Bring to a boil; cook and stir for 1-2 minutes or until thickened. Remove from the heat. Stir in the process cheese until melted. Add macaroni and 1 cup cheddar cheese; mix well.
Spread two-thirds of the macaroni mixture in a 13-in. x 9-in. x 2-in. baking dish coated with nonstick cooking spray. Spread turkey mixture to within 2 inches of edges. Spoon remaining macaroni mixture around edges of pan. Cover and bake at 375° for 30-35 minutes or until bubbly. Uncover; sprinkle with remaining cheddar cheese. Cover and let stand until cheese is melted.