Programmatically marking a thread as read

[benFF]

I'm using the hook "showthread_getinfo" to scan posts in a certain forum when opened, and if they include certain key patterns, using a exec_header_redirect to send them on to the correct place.

This all works fine, however as the hook is called before the page is processed - these threads permanently stay as "unread".

Is there a function I can call before the exec_header_redirect which will mark the thread as read (I'm using DB marking FWIW) so that they won't appear in new posts all the time?

Ta muchly,

Ben