function ConfirmUpdate(){
  
  if(confirm("Your session is about to expire. Press 'OK' to renew your session.")){
 
 window.location.reload(true);
  }
}      
      
var timerObj;
function SetTimer(min){
 
  setTimeout("ConfirmUpdate()",60*min*1000);
  
}
      
//start the timer
//SetTimer(20);