Here you have an example (partial) that is working

CREATE CURSOR Box (box c(10), freezer c(10))
INSERT INTO Box (box, freezer) VALUES ("1","123")
INSERT INTO Box (box, freezer) VALUES ("2","999")
INSERT INTO Box (box, freezer) VALUES ("3","999")
CREATE CURSOR NewLocation (box c(10), freezer c(10))
INSERT INTO NewLocation (box, freezer) VALUES ("2","123")
SELECT Box
UPDATE Box SET freezer = NewLocation.freezer WHERE Box = NewLocation.box

Oscar Zarate
National Australia Bank