Get custom data from choices sheet for calculation

Sorry to zombify this topic, but I am not able to achieve this. I would like to get a value from a column of a list in the choices sheet (not from a extarnal csv file) and I can't. I get no error, no value.

I would like to get, from the "stations" list the value of the column "month_03" for tech selected item.
In the calculation column of my calculate field I have this xpath expression :

instance('stations')/root/item[name=${station}]/month_03