¿¿Special Announcement for closed threads??

[Glas]

well, we had a big meeting with my forum staff today
and we're going to close plenty amounts of threads (from 2009)

Sadly there is a lot of important information, and we can't deal with necroposters

Is there anyway with xthreads or php conditionals if thread closed edit a certain template (header include i though) to show a overlay announcement that follows the screen and says a message?
or a edit at start and end of the page

with the conditional i can continue with the rest i think ^^U

il really appreciate your help guys