I need to update a sub-form with information already preloaded - how can I do that.

I need to update a sub-form with information already preloaded - how can I do that.

Hello everybody, I am trying to create a form of sales order but that contains all the products listed in the products database to enter quantities and calculate the sales order amount. 

I am trying to use sub-forms to do it, but I don´t know how to display (one per row) all the products available in my catalogue. 

Anny suggestion?