[rules-users] How to stop rules

Hello, i want to stop the rule engine when some spezial rules fire. I am working for rules for an online shop. The Problem (example) A rule finds out that we cannot put a book into the onlineshop besause the price is to low, not defined, ....! These rule has a high salience. When this happends we can stop going on and create an error. In javacode i can write my one exception and and throw it. But what can i do in Jboss Rule? Regards & Thanks Stefan