function CreateCenteredDialog(winwidth, winheight, url) {
  winleft=(screen.width/2)-(winwidth/2);
  wintop=(screen.height/2)-(winheight/2)-200;

  win=window.open(url,'','toolbar=no,menubar=no,scrollbars=auto,resizable=yes,height='+winheight+',width='+winwidth+',left='+winleft+',top='+wintop);
  if (win) {
    win.window.focus();
  } else {
    window.showModelessDialog(url,'','dialogWidth:'+winwidth+'px;dialogHeight:'+winheight+'px;status:no;help:no;');
  }
}