In a large saucepan, cook beef and onion over medium heat 6-8 minutes or until meat is no longer pink, breaking into crumbles; drain. Add potatoes, water, celery, bouillon and salt. Bring to a boil. Reduce heat; simmer, covered, 15-20 minutes or until potatoes are tender., In a small bowl, mix flour and 1/2 cup milk until smooth. Stir into beef mixture. Bring to a boil; cook and stir 1-2 minutes or until thickened and bubbly. Stir in remaining milk; heat through. Add cheese; cook and stir until melted.