function validateDate(field)
{
  date = document.getElementById(field).value;
  if (date != undefined)
  {
    var match = date.match(/^(\d\d)?\/(\d\d)?\/(\d\d\d\d)$/);
    if (match != null)
    {
      var md = new Array();
      md['01'] = md['03'] = md['05'] = md['07'] = md['08'] = md['10'] = md['12'] = 31;
      md['04'] = md['06'] = md['09'] = md['11'] = 30;
      md['02'] = (match[3] % 4 == 0) ? 29 : 28; // handle February for leap years

      if (match[1] <= md[match[2]])
      { // day given is less than or equal to max days in month
        document.getElementById('dob_msg').innerHTML = '';
        return;
      }
    }
  }
  if (date != 'dd/mm/yyyy') {
    document.getElementById('dob_msg').innerHTML = '<br />Invalid date - use DD/MM/YYYY format';
  }
}