Creating the login experience with Security Assist would allow you to have the user enter the details once, then so long as they login these details can be retrieved and associated with an order.
Using DataAssist you can insert a record into your db with just about any values, including session variables. If you can access this info on the page and store it in a variable you can use that variable as the value for a column when you insert the order info.
You could have the Security Assist pages for user registration, and add in this network identifier. You can then get the details for the user at any time based on this value, you would need to come up with a way to ensure that the network ID has been associated with a user and if not force them to the registration page.