At the moment there is no dynamic notification mechanism. I have seen a number of feature modification requests to implement such a feature though; perhaps you should join the fray and submit a similar request?
What can be accomplished today, is to devise a custom query - requires SQL know-how - that looks for a specific VirusScan property that each node is reporting back to the server on ASCI (property collection).
<Section name="On-Access General"><Setting name="bEnabled">0</Setting>
This property corresponds to a registry setting on the end client where VirusScan is installed, and for the most part it accurately reflects the state of the On Access Scanner.
There are no default queries to provide you reports on this property, which is where the SQL know-how comes in. I won't be much help there, sorry.