Cook celery, green pepper and onion in butter until tender. Arrange half of the bread slices in bottom of 2-quart baking dish; top with half of the corned beef. Spoon vegetable mixture over corned beef. Cover with remaining corned beef; top with remaining bread. sprinkle top with cheese. Combine milk and eggs; mix well. Carefully pour mixture over bread. Bake in 350°F oven 40 minutes or until golden brown.