Windows 7: Sleep only when task is finished?

My problem is this: I can control wake up, go to sleep, etc. with scheduled tasks and BAT files.

eE.g. one of my BAT files that sets active a power schame with go to sleep 'never' and hibernate 'never' which I created:

@echo on
rem "Always On" Power Scheme
C:\Windows\System32\powercfg.exe /setactive 613f668b-8d6f-4cb5-a271-db1aea4ca4a3

but I don't know when the application (in this case BitDefender Virus Scan) finishes (unless it is a Windows application and have Event ID's). I am trying to use tricks (e.g. when the application writes a log file at the end, etc.) but this doesn't always work. Using the this tutorial, I either leave the computer on too long, or it shuts down too early. (In Windows XP, it always waited for the application to be finished before the "unattended shut down" period kicked in.

I would greatly appreciate any help with this issue.

Thanks,

Laci.