I created a small sample project to demonstrate how to do this. I started with the Event sample app. If you start the app, the home page will have 2 tabs, one for products and one for orders. There are a few data records in the project too. You can download it at this link: http://www.filehosting.org/file/details/690082/EventManager.mpk
Hopefully that will get you started.
Mike's example is great and I have that working, thanks Mike! But, I would still like a list of products to check off and add at once. I've started with the link from my first post but need help with the first step, any tutorials that explain how to do this:
Given what you're trying to do, you can open this page via a microflow that also creates (without commit!) an orderItem for each product, and associates it to order and product.
Once I build this I'll post the entire process on this thread.