Capture browser refresh event in browser script

Hello,

We have put-in custom code in Application browser script to handle user "logging off" by clicking the "X" on the browser. While the custom code works correctly as expected upon user clicking "X" (thus closing the browser / logging off of application), this code also kicks-in if and when user presses function key F5 to refresh the browser.

I would like to know if there is a way to detect the F5 / refresh event and / or how to avoid custom code from kicking in when F5 if pressed.

Thanks

-Lokesh