In A Large Saucepan, Saute Hot Dogs And Onion In Oil Until Onion Is Tender. Sprinkle With Flour, Mustard And Pepper. Stir In Celery, Water And Ketchup Until Blended. Cook And Stir Over Medium Heat For 10 Minutes; Remove From The Heat. Stir In Cheese. Spoon About 1/2 Cup Hot Dog Mixture Into Each Bun.