var navAway = false;

function navAwayCheck(){
   if(navAway)
    {
        if(confirm('Your order is not completed. Leave this page?')==false)
        {
            window.location.href='checkout.aspx';
	        window.navigate('checkout.aspx');            
        }
    }
}

function setNavAway(){
   navAway = false; 
}