You cannot do this with a scan initiated from ePO. However, if you want to bypass a scan, just reboot. Or you can lower the priority from "Below Normal" to "Low" and this should make a scan unnoticable to the user experience.
As I'm not able to have access to an ePO server I'm not able to confirm this, but I believe there's an option for the users to defer the scan within the task configuration in ePO.
Again, not sure, and even if this is true, could've been avaible for previous versions only.
Message was edited by: edxavier on 3/22/13 8:21:08 PM BRT
Defer is only an option just before it runs. Once it is running it cannot be stopped (if ePO managed).