In cocos2d, what is the method to change the anchorPoint and position without causing it to suddenly jump?

Question

In cocos2d, I have a CCLayer that is being moved and scaled using touches and pinch gestures.

By default, the zoom always goes towards the anchorPoint. Changing the anchorPoint fixes my zoom problem, but causes the sprite to suddenly jump.

Here are two similar questions here and here, but I still don't know exactly what to do.

Thanks!