Use the margarine and flour to make a roux that is the color of browned peanut butter. Saute bell pepper, onion, celery and garlic in the hot roux. Stir 5 minutes. Then stir in diced tomatoes and tomato sauce on low heat. Add shrimp and stock. Stir well over low heat.
Add black pepper, red pepper, Worcestershire sauce and sugar. Cook over medium heat for 15 minutes. Turn off heat and add parsley. Serve over fluffy rice.