Copy Purchase category from PO invoices for classification value

Hi community

Any idea how to achive: customer has both PO and non-PO invoices. No items/inventory in use. Taxonomy used for classification is slightly extended PO purchase categories list. I am looking for options to copy PO category from invoice line/PO to the classification value for PO invoices.

Would appreciate any suggestions!

I don't see an attribute to build a rule based on PO category, also don't want to exclude all PO invoices from analysis