I am looking to link flagged emails in Outlook 365 to Planner tasks. The sample Flow "Create planner tasks for flagged emails in Office 365" creates a Planner task from a flagged Outlook email, however upon completing the Planner task, the associated Outlook task remains open. Therefore, I am attempting to extend this flow to capture the Outlook messageId within the Planner task, and then create a second Flow that triggers upon completion of the Planner task, completing the associated Outlook task.
My initial flow:

Can someone help me with the code to extract the string after "OutlookMessageId="so that the second Flow will be able to use it to find the associated Outlook task?
Thanks,
Jim