Peel shrimp, leaving shell on tail section. Lay shrimp on back, split almost through with a sharp knife, (butterfly cut), and devein. Combine onion, celery and margarine in a 1-qt casserole. Microwave on high 3 minutes, or until onion is transparent. Stir in remaining ingredients. Brush the shrimp with melted margarine, and spoon 1 tablespoon of the onion mixture into the butterflied area of the shrimp. Place in a baking dish with the tail resting straight up on the side of the dish and microwave on high 3 minutes or until shrimp are opaque. Do not overcook. Time varies with the size of the shrimp.