Hi Cristobal,
You can use this FM in event 4502, where in you can determine a liability category that is different to the SPRO configuration (Posting area 1251) for an open item.
This is because, in SAP Credit management, the liability category differentiates between different liabilities, such as open items and orders that have not been billed yet.
Apart from the above event, I think you can use this FM in events 1840 and 1841, which gets triggered when you execute FPCM1 for transferring the credit liability.
Hope it helps
Thanks,
Amlan