Hi, I see you are looking for Dolibarr expert to do a little change in Invoice module.
The field that tell if the detail line must not sum to the “Total net of tax” is in the facturedet table, and it is “vat_src_code”. If this field is like “%suplido%” then you must to sum this only at total_ttc, but not in total_ht.
I'm CRM expert. My recent CRM project was https://www.freelancer.com/projects/php-mysql/zencart-dolibarr-connector/
the client needed a program (PHP, MySQL) to connect my Zen Cart online store to my Dolibarr ERP system.
1) When a new user creates an account on the Zen Cart store, a Third Party Contact "Prospect" must be created with the user's provided information.
2) When an order is placed on the Zen Cart store, a New Order Draft must be created with the order information (products, quantity, addresses, etc).