Copy Order Field to a new Custom Field with Snippet

Hi i like to know if its possible to do something like this.

In every order I receive in Woocommerce, I need a Custom Field called “NIM” to be created which is just numbers.

The problem that arises for me is the following.

If someone places an order on my own page, when make checkout, the site ask the client to fill the “NIM” field, so there is no problem with this type of order.

The problem is that I have Woocommerce connected to other sales sites from which they bring me orders, but I can’t make those orders create the “NIM” field

The only i can do is the necessary data for the “NIM” field, be generated in the billing_company field.

There is a way to create a snippet that copies the information from the “billing_company” and create a Custom field called “NIM” with this info.

If that is possible, it is also possible that if the NIM Field is already created, because the client made the direct order on the page, do not delete it with the “billing_company” field

If the Client create an order on the webpage, and complete both, NIM and Billing Company field, how i can tell to the snippet dont copy this time.

Thanks