Hide / Unhide Open Document Link in PO approval notification conditionally

Dear Community Members, I have a requirement to hide "Open Document" link in Standard PO approval notification conditionally. When the Approval notification comes to the approver the "Open Document" link should be available and when approver approves the notification then in the worklist in "All notifications" the link should be hidden. Which means in closed notification the "Open Document" link should hidden. We tried using PO approval workflow customization. But it didn't work. If anyone has done something similar please let me know.