Reducing quantities on sales orders according to delivery notes

Is it possible to adopt the sales orders to reduce by delivery number.
Example, a customer order 10000, I create the order only deliver 5000? When I go back to the order, the original 10000 is still in, I need it to be reduced by the quantity that is been delivered via delivery note? So, I can not duplicate orders, once the total is been delivered, via delivery note the order quantity is reduced to zero.

Please do not divert topics with unrelated questions. This has nothing to do with custom fields. It was moved to its own topic. Read

As you were told before, sales orders have no financial impact. They are unconnected to any other transactions. The functionality you describe is available if you create a sales invoice. Then you will see the undelivered quantity in both the Customers and Inventory Items tabs.

I understand it has no financial implication. My question was is it possible to change it so it reduce the sales order qty?

That would not make any sense from an accounting point of view. If sales orders were linked into the rest of the program the way you describe, reducing the quantity on the sales order would be changing the accounting after the fact. It would reduce the quantity the program calculated was owed to the customer in the first place. By the time everything was delivered, there would be no order left and nothing to invoice.

There has previously been discussion in the forum about integrating sales orders into the workflow to obligate inventory so the same inventory cannot be sold to more than one customer. But that would not include changing the sales order quantities themselves.