In 2 tablespoons oil in same skillet, saute onion and celery until tender (5 minutes). Return eggplant to skillet. Stir in tomato sauce, bring to boiling. Reduce heat. Simmer, covered, 15 minutes. Add vinegar, sugar, capers, salt, pepper and olives. Simmer covered 20 minutes longer (stir occasionally). Refrigerate overnight covered.

To serve: Turn mixture and serve with toast rounds or crackers. (Makes 6-8 appetizer servings.)