If you enter a WBS at header level can it be copied down to the item lines?

We have sales orders which require a WBS to be entered at header level (PS-POSID), and then on order save (VA01), it copies the WBS elements down to the item lines.

Has anyone come across this requirement before and if so, how did you do it?

Is anyone aware of an OSS for this or is it a development?

Thanks!

Rochelle