jquery automatic update two select fields
===

I have two `select` boxes. One with list of Cities and the second one with Districts of Cities. When I chose (by click) the City from the first `select` box in the second box I see districts from selected City. That work perfectly, but when the City is selected automaticly by another script, the list of districts doesn't show - i have to manualy select the city from the list and then the list of districts appear.

Here is my script:

    $.viewMap_get = {
        '0' : $([]),
        'Katowice' : $('#c1a, #c1b, #c6, #c7'),
        'Kraków' : $('#c2a, #c2b, #c6, #c7'),
        'Warszawa' : $('#c3a, #c3b, #c6, #c7'),
        'Wrocław' : $('#c4a, #c4b, #c6, #c7'),
        'Gdańsk' : $('#c5a, #c5b, #c6, #c7'),
    };
    
    $.each($.viewMap_get, function() { this.hide(); });
    $('#get_city_district').hide();
    
    $('#get_car').change(function() {
    // hide all
    $.each($.viewMap_get, function() { this.hide(); });
      $('#get_city_district').hide();
    // show current
    $.viewMap_get[$(this).val()].show();
      $('#get_city_district').show();
      var id = $.viewMap_get[$(this).val()].attr("id");   
      $('#'+id).attr('selected', 'selected');
    });

Could anyone help?