First off, are you sure you know what's up with the clustering? I haven't used it in JBoss but it sounds like you should be able to do what you want from inside the app-server, not at the DB level.
Anyway, you need to look at your commit option. Basically you need to set it to the one that checks the DB at each EJB call, since you have what amounts to an external process changing your data.
This is gonna kill performance though, since JBoss won't be able to do much in the way of caching your CMP beans.
Honestly, if you can I would try to put the clustering at the JBoss level, not at the DB... I would suggest buying the clustering docs and seeing if you really can't cluster CMP beans... The messages I have seen on the dev list suggest that you *can* do that.
I've got the whole docs here. It is not possible to cluster at JBoss level at the moment.
So I'll try to change the commit option. Perhaps it will work....