While pasta is cooking, in 3-quart saucepan, melt butter over low heat. Stir in flour, seasoned salt, mustard, pepper and Worcestershire sauce. Cook over low heat, stirring constantly, until mixture is smooth and bubbly; remove from heat. Stir in milk. Heat to boiling, stirring constantly. Boil and stir 1 minute; remove from heat. Using wire whisk, stir in cheese until melted.