Dynamically fill subform

Dynamically fill subform

Hi,

I'm building a rental system. In this system orders are created of the rented items to a customer. Each order also has a project. One project can have multiple orders.
When the items are returned, a project is selected and then a subform should be filled with all the items on orders in this project. In this subform the returns will be entered and saved.
How can I dynamically build this subform?

Kind regards,

Johan