In a small saucepan, bring rice, broth and water to a boil. Reduce heat; cover and simmer 45-50 minutes or until rice is tender and liquid is absorbed., Preheat oven to 350°. In a large nonstick skillet, saute celery, onion and mushrooms in butter until tender. Stir in soup, salt and rice; transfer to a 3-cup baking dish coated with cooking spray. Cover and bake 25-30 minutes or until heated through.