How to handle swapping items on orders if they go negative (amount)

lynge

I'm sort of new at NAV but have 10+ years experience on other ERP systems (only a couple of years programming experience on NAV and is still learning parts of the application). So let me start by apologizing if this have a trivial solution in the standard application - just let me know what it is :-).


Have anyone successfully changed NAV to allow for:
- Negative Sales Orders to become Posted Sales Credit Notes
- Negative Sales Return Orders to become Posted Sales Invoices
- Negative Purchase Orders to become Posted Purchase Credit Notes
- Negative Purchase Return Orders to become Posted Purchase Invoices


We are trying to find a solution for this scenario:

We have several customers used to handle returned, defective items on regular Sales/Purchase Orders.
They do this by:
1. making a Quantity negative line on an sales order for the returned items. Typically on a RMA location
2. make a shipment on the sales order
3. making a Quantity negative line on an purchase order for the items they need to return to the supplier (also using the RMA location)
4. make a receipt on the purchase order

Now the supplier can choose different actions based on his stock, the item age and whether or not the product/model/version is discontinued.
If he chooses to repair or swap the item - not problem, we just:
5. making a Quantity positive line on an purchase order for the items returned from the supplier (also using the RMA location)
6. make a receipt on the purchase order
7. making a Quantity positive line on an sales order for the items they need to return to the customer (also using the RMA location)
8. make a shipment on the sales order

No problem. Both the purchase and sales will be with 0 amount. This is allowed and will make posted invoices both for the purchase and the sales.
Even if the supplier swaps to something more expensive and the customer agrees to pay the difference, it is no problem. Both purchase and sales will be a posted invoice.

But if the supplier swap to something cheaper - or simply issues a credit memo (and we either chooses to issue a credit memo for the customer or swap to something cheaper) we are i huge problems.
We'll need to reverse the shipments (which is quite a hassle because it might be neede to move settlements on the shipment lines first)
And then we'll need to copy the document to a return order, and then redo the shipment. And then do the posting...
Consider how complex this will be if each order and purchase contains multiple itemnumbers that needs to be handled as part shipments and part posting (because they are returned on different dates from the supplier)
Some will need to be posted as credit notes and some as invoices. So we might need to transfer lines back and forth multiple times...

How would you solve this?

Thank you for any help or clues on how to solve this :-)