Get the latest facebook post comments

I use the api chart to get posts from facebook. By default, facebook provides two comments per post. But lets talk in a few weeks, a comment is made on a very old post. Then how can I get this comment. I mean, I am currently loading a page with posts by page, bookmarks of the last page, from where I read the message data.

So how can I get this comment on an old post. I need to go through the pages to get a comment again or some work so that I can pull out this new comment.

Any suggestions