Preheat oven to 375. Melt butter in a 2 quart saucepan, sauté onion and celery until tender. Stir in flour until smooth. Add seasonings. Gradually add milk and continue to stir until smooth and creamy. (not thick – do not let it boil). Remove from heat, now add lemon juice and ½ cheese. Stir well. Grease (with non-stick cooking spray) an oblong 2qt baking dish. Cover bottom of dish with layer of rice. Cover with shrimp. Cover with sauce. Using a fork, poke down into casserole to make sure sauce gets down onto shrimp and rice. Spread with remaining cheese. Sprinkle with paprika. Bake at 375 about 30 minutes. Serve with salad and veggies.