Restart Conditions for Purchase Order process control workflow

hi, I need to restart the purchase order workflow only when the price is changed. I referred to this thread

https://archive.sap.com/discussions/thread/1775585

for implementing the BADI /SAPSRM/BD_WF_PROCESS_RESTART , I need to check the change docs of the PO.

I saw in FMs BBP_PD_PO_GETDETAIL and BBP_PD_PO_ITEM_GETDETAIL , I did not understand how to check if the price has been changed. How do I detect that?

thanks

bhakti.