Hi
This is not possible in standard SAP. The Inbound/Outbound Delivery field within VL09 is for the SAP delivery number and not the external vendors delivery note number.
To reverse a goods receipt, use MIGO and select Cancel Material Document. When you then enter the GR Doc number, the external delivery note number will be auto populated with the vendors delivery note as entered when carrying out the initial GR.
Cheers
A