Dear all,
Thanks for your answers. The module "Block delivery before payment" solves my problem.
FYI :
When activated, it adds a "Marked As Paid checkbox" (=false) in the Sales Order and another "Sales Order Blocked checkbox" (=true) in the related Delivery Order.
While the "Marked As Paid checkbox" is not manually checked, the "Sales Order Blocked checkbox" stays at true and no delivery is allowed.
Regarding our need, we changed the code to have an automatic check action of the "Marked As Paid checkbox" after the payment of the invoice.
Bye
(Sorry ! No printscreen, my karma is to low at the moment)