REceivables transaction numbering for IC module transactions

We are implementing InterCompany module for many companies of the group in different countries. Each country has a different legal requirement regarding receivables transactions numbering. Most of them can be achieved by copying the document number to transaction number option in receivables transaction source (global intercompany) but in the case of Romania, they transaction numbering is a complement of 3 letters + a sequential number. To achieve this in regular receivables transactions, they are introducing manually in the transaction number the letters, and in document number the sequential one. For reporting purposes, all the reports are taking the combination of