var newWindow = null;

    function closeWin(){
        if (newWindow != null){
            if(!newWindow.closed)
                newWindow.close();
        }
    }
    

function popUp(URL,Type,Height,Width) {
closeWin();
var winOpts="";

if (Type=="stretchy") winOpts="scrollbars,resizable,height="+Height+",width="+Width;
if (Type=="resize") winOpts="resizable,height="+Height+",width="+Width;
if (Type=="noResize") winOpts="status,height="+Height+",width="+Width;

newWindow = window.open(URL, 'newWindow', winOpts);
newWindow.focus();
}