Quick Job - WooCommerce Add Custom Order Field $50 USD

READ FULLY: This is a quick job, price is firm at $50 USD, need turnaround in 2 days or less. We need a piece of code (to put in functions.php) that adds a checkbox (boolean) field to WooCommerce orders, use field name "eco". When the checkbox is selected, we need the /checkout/ page to refresh, similar to the way that it does when you change shipping method. The refresh doesn't need to be ajax, if you have the boolean and then a "Save order" button that refreshes the whole page, that's okay.