Hi Grf, 

Please note that this function has api depends. Which means that it will be triggered when one of the field mentioned in depends ('currency_id', 'date', 'price_total', 'price_average', 'residual') is changed. 

try to add print'0000' inside the function and then change one of the fields, you will see the print result in your logs. If you do not make changes on any of them, you will get no print result in the logs.

Thank you.