function check_form(form)
{
return_boolean = true
 obj = eval(form)
 for(i=0; i < (obj.length) ; i++ )
 {
  field_name = obj.elements[i].name;
  if (field_name.indexOf("_ck") != -1)
  {
    if (obj.elements[i].value == "")
    {

        obj.elements[i].style.backgroundColor = "red";
				obj.elements[i].style.backgroundImage = "url(images/error.gif)";
      return_boolean = false
    }
    else
    {
        obj.elements[i].style.backgroundColor = "white";
				obj.elements[i].style.backgroundImage = "";
    }
  }
 } 
return return_boolean;
}