title: How to update shipping calculations on change of custom shipping field in woocommerce?
body: <p>I have added new custom shipping field ( select option ) to woocommerce checkout page.</p>
  
  <p>I am using that for shipping calculations.</p>
  
  <p>that works perfect as well. but issue is while I change values in that field it do not update instantly.</p>
  
  <p>It gives correct calculations on next page, after page submit.
  I need it to work as change in custom field.</p>
  
  <p>How to trigger WooCommerce Ajax which updates shipping calculation on change of my custom field ? </p>