Update a case property by a hidden value

I have two refrigerators that contain boxes of vaccines.
Sometimes it happens that the boxes from one fridge are transferred to the other.
But by moving a box, I was able to update the stock of the original fridge but the stock of the destination fridge does not update.
I created a calculated field and put this expression (‘casedb’)/casedb/case[@case_type =‘movements’][case_name = #form/destination/frigo_of_destination][stock_boite_zmapp = #case/stock_boite_zmapp + 1]