Combine chicken, 1/4 cup mayonnaise, yogurt, lemon juice, salt, pepper sauce, celery salt and black pepper in bowl. With fork, mash some of chicken against side of bowl. Stir in celery and olives.
Spread each bread slice with about 1/2 tablespoon mayonnaise. Make sandwiches, using 1/4 cup salad for each. Remove crusts. Halve sandwiches diagonally. Wrap in plastic; chill 6 hours. Makes 10 sandwiches.