The heading should read Custom Scripts
On your REMEXEC0= line, end the line with , ASYNC you must do ', ASYNC' the comma separates it from the commandline.
The default action with a script is to run in SYNC mode that waits for the program to exit before moving on. ASYNC will simply launch it and move on straight away.
If you really want to know when the scan is finished then you will need to reduce the scan that you do maybe using /F- to not scan software as an example.
Mark Star - http://www.marxtar.com
Home of Power State Notifier & Wake-On-WAN for LANDesk