How to choose a different page to share each time?

My Pay with a like campaign continues...
I'm trying to customize this plugin a little bit.
I'm allowing my site's members to share in order to see the content. They also have to share each time they refresh, That's working great now.
Now I want to do the following:
When a user returns, see what page he shared, and choose from a list a different page.
Is this possible? If not, is the data stored in the share statistics for the user and can be accessed somehow so I could use it with a custom code?