Hi Phillip,
Currently there isn't a built-in event that triggers in OCUM when max grow size is reached. However, since there is an ONTAP EMS event that triggers when a grow attempt fails, one could subscribe to that EMS event in OCUM by navigating to Configuration -> Manage Events -> Subscribe to EMS Events, and then subscribing to this event:
You would then need to create an alert in OCUM for EMS events.
The downside to this is that you will only be notified when a grow attempt fails instead of when the final successful grow event occurs. Here is a KB that outlines the process of subscribing to EMS events:
https://kb.netapp.com/app/answers/answer_view/a_id/1072320
Here is another KB that might be helpful for understanding what types of autogrow events can be monitored:
https://kb.netapp.com/app/answers/answer_view/a_id/1009162