Cook pasta according to directions. Rinse under cold water and seet aside. Melt butter in a large skillet over medium heat. Add celery, onion, and garlic. Saute 3 minute. Add flour, stir until smooth. Gradually add milk; cook over medium heat stirring constantly until thickened. Stir in cheese until melted. Stir in shrimp, clams, parsley and sherry. Stir in pasta.