function NewWindow(mypage, myname, w, h, scroll) {
var winl = (screen.width - w) / 2;
var wint = (screen.height - h) / 2;
winprops = 'height='+h+',width='+w+',top='+wint+',left='+winl+',scrollbars='+scroll+',resizable'
win = window.open(mypage, myname, winprops)
if (parseInt(navigator.appVersion) >= 4) { win.window.focus(); }
}

var winhandle = null;

function popUp(URL) 
{
  if ((winhandle != null) && (! winhandle.closed)){
    winhandle.location.replace(URL);
  }
  else
  {
    winhandle=window.open(URL, 'imagewin', 'width=1000,height=800,resizable,scrollbars');
  }

  winhandle.focus();
}