function injectcheckBox() {

    var f = $('srchform');
    if (!f) return false;
    var td = f.getElementsByTagName('td');

    
    var checkBox = '\
              <input type="checkbox" name="offeropen" value="open" id="offeropen">\
              <b>Open House</b>';
              
       new Insertion.Bottom(td[0], checkBox); 
     
     $('offeropen').checked = location.href.indexOf('offeropen')!=-1;

}

Event.observe(window, 'load', injectcheckBox);