Restart app

Question

Hi,
I have a small app with 2 forms.  In form 1, I have a set of buttons that when clicked set the navigate URL of a web browser control in form2, show form 2 and hide form 1. The web pages shown in web browser might require the user to sign in to perform some tasks. I have a button on form 2 that allows user to go back to form 1.
The problem is that if a user logs in while in form 2 and then clicks the button to go back to form 1 (without logging out) and leaves, the next user has access to his credentials. The only way (I can think of) is to restart the application after x minutes of inactivity or if user just click on "Back" button. How can I accomplish this?
This is a desktop app that is used internally in many sites/locations. The application is always on and running.