function setDays(form_name,field_dd,field_mm,field_yy) {
	//alert(form_name)
	//alert(field);
  var y = document.forms[form_name].elements[field_yy].options[document.forms[form_name].elements[field_yy].selectedIndex].value;
  var m = document.forms[form_name].elements[field_mm].selectedIndex;
  var d;


  // find number of days in current month
  if ( (m == 3) || (m == 5) || (m == 8) || (m == 10) ) {
    days = 30;
  }
  else if (m == 1) {
    // check for leapyear - Any year divisible by 4, except those divisible by 100 (but NOT 400)
    if ( (Math.floor(y/4) == (y/4)) && ((Math.floor(y/100) != (y/100)) || (Math.floor(y/400) == (y/400))) )
      days = 29
    else
      days = 28
  }
  else {
    days = 31;
  }


  // if (days in new month > current days) then we must add the extra days
  if (days > document.forms[form_name].elements[field_dd].length) {
    for (i = document.forms[form_name].elements[field_dd].length; i < days; i++) {
      document.forms[form_name].elements[field_dd].length = days;
      document.forms[form_name].elements[field_dd].options[i].text = i + 1;
      document.forms[form_name].elements[field_dd].options[i].value = i + 1;
    }
  }

  
  // if (days in new month < current days) then we must delete the extra days
  if (days < document.forms[form_name].elements[field_dd].length) {
    document.forms[form_name].elements[field_dd].length = days;
    if (document.forms[form_name].elements[field_dd].selectedIndex == -1) 
      document.forms[form_name].elements[field_dd].selectedIndex = days - 1;
  }

}