How do I override the default behavior of select: within jQuery UI Autocomplete?

I have the following:

$('#<%=txtCity.ClientID%>').autocomplete({
  source: function (request, response) {
    var parameters = {
      isoalpha2: '<%=Session["BusinessCountry"].ToString()%>',
      prefixText: request.term
    };
    $.ajax({
      url: '<%=ResolveUrl("~/AtomicService/Assets.asmx/GetCitiesWithState")%>',
      type: 'POST',
      dataType: 'json',
      contentType: 'application/json; charset=utf-8',
      data: JSON.stringify(parameters),
      success: function (data) {
        response($.each(data.d, function (index, value) {
          return {
            label: value.slice(value.indexOf(',')),
            value: parseInt(value.split(',')[0])
          }
        }));
      }

    });
  },
  minLength: 2,
  delay: 50,
  select: function (event, ui) {
    var city = ui.item.label.split(',')[0];
    var state = ui.item.label.split(',')[1];
    alert(city);
    alert(state);
    $('#<%=txtCity.ClientID%>').val(city);
    $('#<%=txtState.ClientID%>').val(state);
  },
});

It's all happy days, except when I select an item from the autocomplete list I'd like to not have autocomplete populate the $('#<%=txtCity.ClientID%>') element. How do I do it? I saw .insertAfter, is that something I should look at?

Help appreciated.