SharePoint Online Expert Developer Needed

I have a SharePoint Online site and I need to show a disclaimer message upon initial login. The user should be able to log in, see the pop up (which can display data from a SharePoint page) and either click "Accept" or "Cancel". If the user clicks Accept then he can view the site, if the user clicks cancel then we should log them out. Once the user clicks Accept then they should not see the message again until they have a new session where they log in t SharePoint Online again. Should be a simple project for the right person.