function windowpop()
{
  tour = document.getElementById('tourselect');
  xpos = (screen.width - 600) / 2;
  ypos = (screen.height - 400) /2;
  
  file = tour[tour.selectedIndex].value;
  if(!file || file == "")
  {
    alert("Please select a tour.");
    return;
  }
  else
  {
    link = "http://www.carlsonrealestate.biz/tours/viewer.html?file="+file;
    var popWindow = window.open(link,"windowpop",'left='+xpos+',top='+ypos+',toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=0,resizable=0,width=600,height=400');
  }  
}