CRM form title change

Hi,

i need to change the form title which the crm system will auto generate and save it permanentlywith one of the fields value  (ur-13)

 i used these script but not working

 Xrm.Page.getAttribute("ticketnumber").setValue(concatenatedString);

                  (or)

document.getElementById("form_title_div").childNodes[2].childNodes[0].innerHtml=concatenatedString;

 Any help.

Thanks

Gary