So I have the following lists:

Facture: ID (Text), Date (Date)
Ligne_Facture: ID_Facture (Lookup pointing to the ID of the list Facture), ID_Produit (Another lookup), Number (Number), total price (Number).

So what I want is to have a page containing the following style of forms: the field ID on the top refering to the ID of the list "Facture" and a grid to fill the list "Ligne_Facture" (the field ID_Facture is automatically the one I just filled and the others are filled manually). Once I save I fill the two Lists. Since I'm a total newbie I wanted to ask you about the right procedures to do so. Thanks in advance, i really appreciate any intervention.