In 1 quart microwavable casserole, combine carrot, onion, celery and margarine. Cover and microwave on high (100 percent) 1 minute. Add broth and 1/2 cup water. Stir to combine. Cover and microwave on high 5 minutes. Stir in noodles; cover and microwave on medium (50 percent) 3 minutes, stirring every minute. Let stand 2 minutes, until noodles are softened.