Well, i found a solution. To answer my own question.
: Yes, you can trigger based on screensaver.
You can, but the screen saver event is not logged by default. To enable logging you need to run gpedit.msc (Local Group Policy Editor). Navigate to Computer configuration > Windows Settings > Advanced Audit Policy Configuration > System Audit Policies > Logon/Logoff
. Then in "Audit Other Logon/Logoff Event
" check the box for Sucess. Doing so will enable Event logging for the screensaver so you can use it with task scheduler to trigger on the eventID 4802
which occurs when the screensaver starts. For more info
Now my sync utility will run when the screensaver is initialized. I can now watch my movies in peace without being interrupted.