Restricting openID logins

Here is my requirement. I want to let users access some of my restricted pages (I have already created a template to check if the user is logged in to see that page) using OpenID, but I want to approve the access the first time they login with their OpneID, before they can login and view the pages. I have installed the RPX plugin which lets users login using their OpenIDs including GMail, Yahoo etc., but I don’t see an option in that plugin to restrict who can login. I don’t want anyone with OpenID to see the pages. I want only the people I approve, but I don’t want them to create a new account in my site. Any help would be appreciated.