Hi Christophe,
as written above: If that isn't sufficient, you could check, if BAdI SPC_POSTING_CONTROL is solving your problem.
This BAdI is processed at the end of retail pricing before the condition records are written to the database. What I definitely know is, that you can exclude conditions to be saved in that BAdI. You have to check if you also can add somehow the raw value you want to save.
Regards
Tobias