Can I use Google Alerts w a vBulletin subforum?

Yes, I can use Google Alerts with a site that has vBulletin - that's not what I'm having trouble with though; I'm struggling with just using Google Alerts to monitor a specific subforum in a forum.

Let's be specific: I'm a musician and I frequent a guitar forum at http://acousticguitarforum.com/. Whenever I'm looking to buy some new gear, I have to manually check the "Classifieds" section which is a "For sale" by members.

url: http://www.acousticguitarforum.com/forums/forumdisplay.php?s=3282a00188c7c9118d80190931a04f37&f=17

The problem: This is a very active forum and Google Alerts doesn't allow me to just filter just down to the subforum level. If I want to monitor for "914ce", for example, I have to monitor the entire site or none at all.

Is there a way to monitor just the subforum?