var updateEvery = 900;   // 900 Seconds = 15 Minutes
function SessionRenew( )
{
    timer=setTimeout( 'SessionUpdate( )', 1000 * updateEvery )
}
function SessionUpdate( )
{
    document.getElementById( 'SessionRenew' ).ImageRenew.src ='../../WebMainDirs/JS/SessionRenew.php';
    SessionRenew( );
}
SessionRenew( );