Combine flour, salt, pepper, and 1 cup of milk. Stir until smooth. Combine cheese spread and remaining milk in top of a double boiler, cook over hot water until cheese melts. Add flour mixture and hot sauce to cheese mixture, stir until smooth. Add shrimp and crabmeat. Pour into a greased 1 1/2 quart casserole dish and top with shredded cheese. Bake at 350 degrees for 20 minutes. Serve over hot cooked rice.