Idoc Type to add a new line item to existing Inbound delivery

Hi Friends,

we have one requirement.

In the system Inbound delivery is created through Idoc. Once the inbound delivery is created, we need to change that inbound delivery by adding a new line item to that inbound delivery where the line item belongs to another PO. Means, I have an existing inbound delivery number for a PO having one line item. Now I want to add another line item into the inbound delivery for another PO. I have created the inbound delivery through Idoc using the idoc type DESADV. Now I want to change the inbound delivery for adding the line item. Can anybody please tell me which idoc type should I use for this above highlighted requirement?

Thanks & Regards

Satya