Hi Viktor,
Can you check this if this works in your scenario :
CRM->Transactions->Settings for Service Requests->Settings for Processing Log
Or
Use Transaction SCDO and create a new Object which in turn will create a FM. Use this where ever changes are going on for the New Field. This will in turn update the CDHDR and CDPOS table.
Or
Mark the respective field in the data element to store the history.
Hope this helps.
Thanks,
Samantak.