Change Naming Series for Amended Document

Hi All! What is the best way to change naming series for an amended document? Currently it will just add “-(incremental number)” from the cancelled name. I want to add letter it that is okay. Any help is greatly appreciated. Thanks!

For this, I got this workaround. Needed to add new PO Name field just to not alter the Primary Key (“name”) and added a validation:

self.po_name =
if (self.amended_from):
        rev_name = str(self.po_name)
        if not (rev_name[15:17] == "REV"):
             new_name = rev_name[:14] + "-REV" + rev_name[14:]
             self.po_name = new_name

I will close this. Thanks!