Transfer custom fields from SalesHeader / Detail to Invoice

Hi Everyone,

I have 3 custom fields on the sales header (SORDER) and sales lines (SORDERP).  I also have the same fields on the invoice tables.  When the order is invoiced I would like to transfer the values of these fields from the order to the corresponding invoice.  I imagine I would need to create an entry point but I'm really not sure where or which one I should use.  I'm relatively new to Sage X3 and I'm not looking for a detailed answer as I like to figure things out on my own but if someone can point me in the right direction it would be greatly appreciated.

Thank you very much in advance,