In large skillet, spray pan with nonstick cooking spray (or use the 1 tablespoon margarine or butter) and saute onion, garlic, green pepper, and celery for about 5 minutes or until tender. Remove from heat. Stir in tomato sauce, tomatoes, water, bay leaf, parsley, salt, pepper, flour, Tabasco and chili powder. Simmer 10 minutes. Add shrimp. Bring mixture to a boil; cook covered over medium heat for 5 minutes. Serve Shrimp Creole over rice.