function isAlphaNumeric(theElement, theElementName)
{
  var s = theElement.value;
  var filter=/^[a-zA-Z0-9]{1,}$/;
  if (s.length == 0 ) return true;
  if (filter.test(s))  
       return true;
  else  
         alert(" Please input a valid AlphaNumeric Value!" );
    theElement.focus(); 
    theElement.select(); 
    return false;
}