duplicate workflow instance

I have this requirement, where client wants the opportunity close date to automatically roll into the next quarter, when the next quarter comes, and the opportunity is still open.

My approach was to calculate the next quarter date, and wait until that next quarter date and update the date forward,

the workflow will trigger again when the date is updated, and keeps it rolling forward (on record modification, close date <> pre close(date), stage=open)

it seems to work, but my issue is when the user goes in and modifies the date outside of the automated date rolling => it will also fire the same workflow, giving me