$(document).ready(function($) {
$("#ctl00_cphBody_wzdRegister_txtPostCode").change(function() {
$('##ctl00_cphBody_wzdRegister_ddlSubub >option').remove();
  $('#ctl00_cphBody_wzdRegister_ddlSubub').append($('<option></option>').val("").html("Loading…"));
  });
});