Reward system for members sharing website via fb or twitter

Hi there

I was just wondering if anyone new of a way of creating or buying a reward scheme for someone who shares pages or images on there facebook or twitter. The way it would work is
1.) customer logs in to there account on my site
2.) they then go to a product on the site or a page which have share buttons
3.) they press share on image or page which takes them to fb or twitter
4.) once they share on fb or twitter it adds reward points to there account.

I have seen this work on a site but it adds reward points when the customer presses the share button on your site but they don't have to press it on fb or javascript.

Would prefer top option but could also live with bottom option so if someone knows of. A way or would be willing to pay for an extension

Thanks

the first one in the result should do what you need. Facebook share, shares for a coupon: http://www.opencart.com/index.php?route ... ok%20share