Change Empties article in PO

Hi,

We have a scenario of empties in PO. PO is created with main article and empties is updated.Now the Problem is when we want to change the main article to other article which has different empty article attached.The PO is not updated.we cannot change the line item as it is linked with sales order.

How can we replace empties in ME22N

Thanks

Sachin Sonkar