If an user is member of a specific group I want the user to open a new tab with the given link. I do only want this to happen once, so I want it to store a cookie when it open a new tab for the user and next time check if the user have the cookie or not. I hope this is understandable and possible. How do I do it, is it hard? I can reward with 10 mBTC for the code if it is legal here.