I think you’re expecting something that you can’t truly do with Perspective at this time.
If you’re determining which just what page (pageA or pageB) to show a person, there are ways to do that, but you have to understand that Perspective does not open to the same page every time; depending on browser bookmarks or links or history, a user could open a new session onto any page in your Perspective Project.
There are Session Events in Perspective, but Session Startup is invoked before a user has even logged in or a page has been opened, so you can’t use it to manipulate pages. View Startup Events could possibly be used for something like this, but you’re reliant on a user reaching the Page which uses that View. We have incoming Page Startup Events which have the same drawback. There is an open feature request to determine navigation after login based on some logic which is exactly what you’re looking for (for authenticated users, so you would need to require authentication for your project) but that feature is not in development yet.