I'm not sure how Avast works, but with Avria version 9, I just navigate to the File and right-Click on the File and Select
Scan selected Files with Antivir. You would think Avast would have something similar?
I've looked on Google about Avast's Scanning method and I think you will have to look in Avasts settings to get a pop-up to tell you the results of the Scan, however if you should have a Virus, it's supposed to give you an alert sound.
If you were to get a Virus, just leave it there and let Sandboxie Delete the Sandbox.
One more thing. Even though the Virus will be Deleted, If avast detected it, it might have Quarantined it in Avasts Quarantine Folder. Don't worry about this. That Virus can't harm your computer in any way, and you can just remove the entry from Avast. You might also find that Avast will find a
"Virus" in the
System Restore when you Scan later. Not to Worry I'm told. That's just a
"Windows thing" That can't hurt your Computer either. It's just another
neutered copy of that Virus. Just Delete that System Restore point so you won't get anymore notifications from your Anti-virus Scanner.
Ken:

System Specs: = Win XP SP2 (32bit),[OutLook Express 6.] [ FireFox 19.0, - NoScript, - Sandboxie 3.76 - 32 bit, - FireWall - Comodo 5.3 ]