Change Shopping Cart and update Purchase Order

Hi experts

i'd like to know if there is a way in order to change a Shopping Cart "father" of an existing Purchase Order and update the same PO.

The issue is that if i change on ECC 6.0 the PO, adding for example a new line, the goods receivement gets an error.

So i thought to change, first of all, the Shopping Cart and then update the existing PO in order to have a correct goods receivement. Is there a way to do that?

with kind regards

andrea