Show last post of previous page as first on next?

[ia7]

Hi vB coding gurus, I have a question that's probably been asked maybe a number of times (a google search is hard to get right).

Is it possible to create a plug-in that will make 'showthread' show the last post of the previous page as the first post on the next page?

Example: Say 20 posts per page. I want that 20th post to show as the first post on Page 2 and so on. Why? Well as you get on a bit you forget what you saw 5secs earlier and so having that topic of discussion being readily available will make it easier to continue it on... hopefully!

I'm not looking for a global first page or anything, I've already seen them.

I had a look at showthread.php but it made me cry a little so I'm asking you, the wise ones, if this is possible to do and how.

Thanks.