Hi Dave,
I'm not an AS specialist but before someone more competent chimes in I'd suggest you take a look in the following plugins:
- http://anonsvn.jboss.org/repos/jbosstools/trunk/as/plugins/org.jboss.ide.eclipse.as.ui/
- http://anonsvn.jboss.org/repos/jbosstools/trunk/as/plugins/org.jboss.ide.eclipse.as.core/
You might want to join the #jbosstools channel on irc.freenode.net and address your question to rawbdor or adietish.
Cheers,
Koen