Preheat oven to 350 degrees. Trim tops from celery; cut celery in 1-inch pieces. In 10-inch skillet, melt margarine. Add carrots, green pepper, onion and celery; saute for 5 minutes. Spoon into a 12 x 8 x 2-inch baking pan or 2-quart casserole. Stir in tomatoes. In a small bowl, mix cornstarch and chicken broth until blended; stir in parsley and basil. Pour over vegetables. Cover and bake until celery is tender, about 45 minutes. Serves 6. Note: Canned tomatoes may be used instead of fresh tomatoes.