how to bulk update the notification controls for purchase agreements

We would like to set 2 reminder notifications to be sent to contract managers one to be sent before 90 days and the other 180 days before expiry for all the agreements . I have checked the contract type task but one can only set specific days either 90 or 180 in the days of expiration feild.

Could you please advise how to bulk update the notification controls to set 2 reminders before expiry on all the agreements.