Disabling refresh

i have developed an online exam system. when a user clicks on the "Start Test" button, the timer starts at the top of the page and questions are generated.

Now if the users refreshes the page, timer starts again and new set of questions come up (since of i have used random generation logic) .

i want users not to be able to refresh this page (disable refresh) so that timer should countdown till the end and for questions only one set of questions for one user be generated.

Any suggestions for this problem would be helpful.

Thanks in advance.

You cannot successfully disable refresh in a cross-browser manner. And you shouldn't. See InterfaceDesignersRule1.

What you should do is to track the state of the exam and the timer in the session (most likely employing Ajax to send the state to the server periodically). That way, when the user refreshes, you can detect that they were in the middle of an exam, and restore the state at the time of the refresh.