Benefits coverage end date

I have a benefit plan that requires approval of a certificate. The certificate can be approved with a date after the event. In this situation, the end date of the previous plan option is being recorded with the date before the event. It must be recorded with the date prior to the day of approval.
Which parameter should I use in this situation?
I have attached a pdf with the step-by-step instructions.
If anyone can help me, I would be very grateful.