ottolo123 on "woocommerce custom invoice date editable in order admin backend"

Im trying to mod woocommerce to adapt it to the italian law. Until now i managed to adapt a lot of things. Im searching a way like the customer note field but aditionally to it i would like to insert a custom date which afterwards we can use to generate the invoice, so the order date should remain the order date and we have a custom manually editable invoice date. Until now i havent found a solution! Could anyone help me?
TThanks max