Bump ads to top in Classipress + Simple Plugin

I have a ClassiPress website and want to utilise a plugin to allow authors to bump their ads to the top for a small fee as and when they wish. There is an existing plugin that claims to do this, however it does not work. I will need you to make a plugin that works using paypal and paypal sandbox mode methods. This function should only be seen by the current user of the ad to be bumped and when they are logged in and no one else. I have also rewritten another function and wish this to be implemented into a separate plugin so that I can switch it on and off at will. I can provide existing files for this to the successful applicant.