Cook celery and onion in large skillet in margarine over medium heat until tender, about 5 minutes. Remove from heat and stir in the sage, pepper, and poultry seasoning. Combine eggs, celery mixture, cornbread and bread cubes in an extra large bowl. Stir in enough chicken broth to moisten. Bake in a covered, greased 2 quart casserole dish at 350 degrees for approximately 45 minutes. Makes 10-12 servings.