Method which triggers after change in shipping address

Is there any knockout method which is triggering after update/edit shipping address on checkout ?

to be in details what I want to achieve is based on city enter, I want to show custom content.
All this working fine when customer has saved address in account but not when customer placing an order first time.

Layout code looks like:

<item name="shippingAdditional" xsi:type="array">
      <item name="component" xsi:type="string">uiComponent</item>
            <item name="displayArea" xsi:type="string">shippingAdditional</item>
                  <item name="children" xsi:type="array">
                        <item name="additional_block" xsi:type="array">
                              <item name="component" xsi:type="string">Vendor_Module/js/view/checkout/shipping/additional-block</item>
                        </item>
            </item>
     </item>

Here’s JS file:

define([
    'uiComponent',
    'Magento_Checkout/js/model/quote',
    'mage/url',
    'knockout',
    'jquery'

], function (Component, quote, url, ko, $) {
    'use strict';

    var content = window.checkoutConfig.shipping_method_promotion;
    var status = ko.observable(window.checkoutConfig.dd_status);
    var earliestDeliveryCityLIst = window.checkoutConfig.dd_earliest_city_list;
    var earliestDeliveryCityTime = ko.observable(window.checkoutConfig.dd_earliest_city_time);
    var longetDeliveryCityList = window.checkoutConfig.dd_longer_city_list;
    var longerDeliveryCityTime = window.checkoutConfig.dd_longer_city_time;

    return Component.extend({
       defaults: {
           template: 'Vendor_Module/checkout/shipping/additional-block'
       },
       getCityName: function () {
       var deliveryDays = '';
       $(document).on('change',".city_dropdown",function(){
            console.log('change event listened');
        });
      return deliveryDays;
    },
     getDeliveryDate: function () {
           var cities = earliestDeliveryCityLIst.split(",");
            if ($.inArray(this.getCityName().toLowerCase(),cities) != -1) {
               return earliestDeliveryCityTime;
            } else {
                return content;
            }
        }
    });
});

Template:

Above attempt is working as expected in case of saved address for customer not for new order.

I know that I can write one more method in JS to listen on change method but how can i pass the value to ko template whenver change happened!?

My bad if you expert noticed any silly mistake i feel approch i used in somewhere incorrect.
Any suggestions !?