In frying pan, cook chicken, onion, green pepper, salt and pepper in butter. In separate pan, cook macaroni; just before macaroni is cooked, add frozen broccoli and bring to a boil. Cook 4 - 5 minutes. To chicken mixture, add cream of chicken soup and milk over medium heat. Heat for 15 minutes. Add 1 cup cheese, stir until thick. Strain macaroni and brococoi mixture. Mix everything together in a 9x13 casserole dish, cover with 1/2 cup cheese. Cover and bake at 350°F for 30 minutes or until cheese is melted.