Transfer order financial voucher for item transfers between sites

Hi experts,

When we create a transfer order for item transfers between different sites, upon receiving the order, a financial voucher is created. This creates a record in GeneralJournalAccountEntryTable. On this table , we have a field for ledger account which is a combination of Main account and default financial dimension values. I want to change one of the default fin dim values through code and generate overwrite this ledger account value before it gets inserted. Can someone point me towards the classes I should be looking into for this ? 

Thanks a lot for help !