title: Woocommerce hook for order update
body: <p>Good morning everyone.
  As the title says I'm trying to fire a function when an order is updated.
  More specifically I want to run this function when a custom field in the order page (admin side) is changed and then saved.</p>
  
  <p>I'm not looking to find out when an order is complete or when its status is updated, but just when this field is updated.</p>
  
  <p>Currently I'm using <code>woocommerce_process_shop_order_meta</code> hook but it doesn't seem to work.</p>
  
  <p>Any advice?<br>
  Thank you!</p>
  
  <p>-- EDIT --</p>
  
  <p><code>woocommerce_process_shop_order_meta</code> is the righ hook to use, I was having an error in the function triggered by this hook so if you ever need to run a function after you click update order in the admin page this is the right way to do it.</p>