Hi i am also facing problem
Have a look at http://wiki.jboss.org/wiki/Wiki.jsp?page=JBossHA.
Afaik, there is no policy that determines the actual load on the server (like % of cpu usage or so, since this is os specific), if you need something like that you would need to write your own loadbalancing policy.
I have had a short look into that, the problem you might be facing is how to determine the load of the machine. Solutions tend to get very OS specific.
There could be better and easier ways that I don?t know of, I haven?t had a deep look into this, but for a starting point: