Add a few things to a custom plugin -- 2

Hi I have a custom forms plugin for vBulletin for a sales forum so when users create a thread they have to fill all the fields. The thread is automatically closed and after 60 days the post is automatically deleted. I need you to allow the user who created the thread to reply it and restart the thread deletion time so, if the user replies the thread the days count will be reset. The purpose of this is that if the user doesn't sell the item he can avoid the thread deletion (reset the days count) just replying the thread. Thanks