Process to "Unsync" select tasks

So, we have on auto-sync (when it's fixed). There are times where our CSMs use a CTA status of Not Valid because they believe the CTA generated in error. We'd like to be able to have a process that unsyncs the tasks for that CTA from SF without the CSM or someone having to manually do it. I thought it might be possible to do from the Rules Engine, but I'm not having any luck. Best I can put together is that since I'm trying to interact with the task in GS, there's not a way I can tell it to make the Auto-Sync false in the Set up Actions. Any suggestions?