Setting the Protected Page Cookie Expiry Time

Hi All

I need to shorten the expiry time of the Protected Page cookie so that a user has to enter the password every time they try to enter a Protected Page. I have been able to successfully change the code in code line 399 of the wp-login.php file such that the expiry time was set to 10 seconds and this works exactly the way I want it to.

The down side will be that if the WP engine is updated, the change will be over written and it will have to be re-done.

From my research many people want to do the same thing, but so far the everybody seems to suggest the above approach, which in my opinion is not a good way to go because of the update issues.

I did come across a couple of plugins but they did not support WP 3.5.2 and had not been updated for over a year,

I did find a recent plugin that reset the time to something less than the current time, but lost the link – I should have installed it immediately instead of continuing to look.

Does anyone know of a Plugin that will set the Protected Page cookie to a short time.

Thanks, Jayne