Ok, so I will answer myself
found the info here:
https://docs.larian.game/Osiris/Shared/DB_DialogMoneyTransfer1/ create an osiris story, or use one you already created, or whatever.
2/ in the init section, type something like:
DB_DialogMoneyTransfer(1,"fron_master_tracker",100);
3/ in the dialogue (in this case, "fron_master_tracker"), insert (in the "flags to check" cell) this script tag when you want a gold check condition : "GEN_CheckMagicPocketGold"
the amount of gold that will be checked, in my example, is 100.
4/ in the same dialogue node, insert "GEN_TransferNPCPayment" (in the "flag to set" cell) when you want the gold to be transfered. Beware, this is a character tag, you will have to write it yourself, it doesn't appear in a list (at least that's what I add to do...).
In my example, the amount of transfered gold will be 100.
Tadaaa.
There is a little more to it, but the wiki page is pretty well explained.
Enjoy you modding, fellow modders
