var win = null;
function NewWindow(mypage,myname,w,h,scroll){
windowClose();
LeftPosition = (screen.width) ? (screen.width-w)/2 : 0;
TopPosition = (screen.height) ? (screen.height-h)/2 : 0;
settings =
'height='+h+',width='+w+',top='+TopPosition+',left='+LeftPosition+',scrollbars='+scroll+',resizable'
win = window.open(mypage,myname,settings)
}

onunload=windowClose;

var win = null;
function windowClose(){
if (win && win.open) {
win.close()
}
}