upgrading membership

I have a subscription plan that offers a discount only to senior subscribers who we have personally approved. I would like existing subscribers with that plan to be able to renew their subscriptions, but do not wish other subscribers or the public to be able to renew on this plan. How can I restrict access to this renew option only to subscribers of the senior plan.
Thank you

Hi Tim

Unfortunately, the system doesn't support this kind of restriction. So if you want to restrict, you will need to customize the code (or hire someone to customize it for you).

Regards,

Tuan