Design Advice

Forgive me if this should be in a different forum.

To clarify, this is a data entry form not a customer order form.

I am creating a Insert page for an order form and I want advice as to which way is best to proceed. What I need to accomplish is have the form collect the order information and submit it to the database as well as send an email with the details for processing. This is easy. Here's where I need the advice:

I have a table that collects the order info such as order #, date, customer info, delivery info, etc. I did not add the item info to this table as there will most likely be many items in each order so I need this part dynamic so I figured I'd join a second table called items for this purpose. So in the order form how would I go about doing this best?

1. Have a two step process where the first step adds the order, shipping and customer info and then have a second step where I have to choose the order number from a list and add the items to it?

OR

2. Have one form where I add all the customer info and a second form where I add the items where one button sends both forms to the tables?

Either way I go, I need to know how to go about inserting additional items without refreshing the page. Meaning if I have a second+ item to add I want to click a button/link that adds another set of fields so I can add multiple rows in the items table at the same time with the same order number.

Make sense? I don't know which is most efficient and least difficult.

All help is greatly appreciated. Leads to tutorials are helpful as well.