[Logician]

In vbulletin, while sending PM, there is an "verify" box which pre-checks if pm receiver can receive your pm. (nice hack btw!) I'm planning to add a similiar "verify" form button next to NEW THREAD Subject forum and by clicking it, you can search if subject of your message matches with any existing board message before sending. But it's not a very easy hack to code (not design, but for security and performance reasons) so I cant promise it will be finished soon. Maybe it can help you a bit.

IMO your exact request can not be done. It's not easy for a hack to identify correct keywords in a message and it's even harder to check the entire database with these keywords without decreasing MYSQL performance. An "light" version can be coded but will not be very succesful, on the other hand a well-coded hack will be hard to design and will effect your db performance.

Maybe you should insistently request your members to use the search before creating a new thread. You can design Mandotary pause warnings, java alert etc to get their attention if sticky threads do not work..

Regards,
Logician