Not really knowing how AVG works, but maybe their definitions have an extension that you can scan on? Or maybe there's a registry that you can read where they keep that info?
Both you can add to the normal scan by editing the LDAPPL3 template in the LDLOGON.
Automatic detection from the inventory is controlled by ldavhlpr.dll. I don't believe that the AVG is supported. So if you want builtin support you will have to enter an ER. These items change with version of LANDesk, so if you are running the latest version 8.8 and AVG is not recognized, then you you will have to enter an ER.
The other way is via ldappl and finding all the registry keys for AVG.