aslamdoctor 0 Newbie Poster

I am using buddypress plugin on my wordpress project to create a social networking site. I have created a User login module & also used a plugin called BP-FBConnect to allow users to log in as facebook users.
So here there are 2 user categories
1. Site Users
2. Facebook

Both users can post articles on site by logging in. Now what I want to do is, any user should be able to share their posts on their Facebook Account Wall. Even they are logged in as Site User or Facebook User. If I am logged in as facebook user, then it would be easy to add an API code to post on wall. But if I am logged in as Site user, there should be some way to post the article on Facebook account by separately logging & keeping the Site User Login active.

Any suggestion regarding that?