Automatically update stock levels

[Danniel Pizatto]

Hi everyone!

In first place, I know that is a lot of invoicing systems topics and examples around, but none of them have a simple functionality that I'd like to add to my company's system.

I need to do the following: everytime an item is added to the invoice, the stock level is decreased by the quantity sold.

I've tried some solutions like Sum(quantity) but it do not work as I expected

Anybody has a simple solution to do this? I do not want to run a script triggered by the user, to avoid errors...

This is a small example of the tables and fields. Any suggestion is welcome.

invoice_stock_example.zip