Automation - Updating Date Field

I am trying to create an automation that will create a new task once a task is completed.  The same task needs to be done every 2 weeks.  When the old task status moved to closed, I would like to copy that record with the same Task Name and Task Analyst and advanced the Due Date to 2 weeks past the Due Date in the old task. 

That's the part I'm having trouble with, not sure how I can tell the automation to modify the Due Date field of the new record to a date that is 14 days in the future of the date in the previous Due Date.


Any assistance would be greatly appreciated.

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Stephanie
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