Magento

I would like to implement in my shop a customer loyalty/fidelization program. For example:
5% discount on second purchase;
7% discount on the third purchase;
10% discount on the fourth purchase;

In Magento Connect, there is some extension to make something like this?

if yes, I can adapt it.

Sorry for my english, I am from Brazil.

Best Regards.

Have you looked at http://www.magentocommerce.com/extension/1261/loyalty-program ?