How can I wipe a users session but still show them a dynamic page?

I have a requirement where a journey is completed in a Mendix app, but on completion I have to redirect to an external non Mendix app. The URL of this external app is dynamic. The users data has to retained in Mendix so they can log in again in future to retrieve it. At the moment I am achieving this showing a page with the redirect widget on it, passing in the URL to the external app. This means a user can press their back button and get back to the Mendix app. I have been asked to make this impossible. My current approach is to capture the SessionID before showing the redirect page and store this in an entity. I then have a scheduled event running every minute looking for these entities and deleting the Session associated with them. This means the session is still valid for up to a minute before being invalidated, which is unacceptable. I did look at wiping it in the microflow that shows the redirect page, but as this is dynamic I can't then show a page. I also looked at trying to create a new User and assigning the session to them before trying to show the redirect page, but this didn't work. Does anyone have any suggestions or a better approach I can take to solve this?
1 answers

Microflow timer widget on the page with the redirect that kills the session? This way the session is always killed after the redirect.