Unable to enter SC vendor as Delivery address in Third party procurement

Hi all,

Im creating a Third party Purchase order against sales order i.e. Account assignemnt cat as E and Item cat as S.

But my delivery address is my subcontractor. In item details Delivery Address tab if I enter the Vendor number and Put a tick mark on SC vendor, when I do GR against this order Stock will will be posted to Subcontracting vendor stock.

But in Third party PO tht tick mark is in display mode.

If I create Purchase Order without account assignment and Item cat Im able to select the SC vendor field.

I checked the screen lay out Account assignment E tht field is optional entry.

regards

Durga Ram

can any one tell me wht configs I missed ?