Hola!
Prueba a creartelo así:
Código:
SET TERM ;^
CREATE TRIGGER PROPAGAR_BORRADO_LALBARANES FOR ALBARANES
ACTIVE BEFORE DELETE POSITION 0 AS
BEGIN
DELETE FROM LINEAALBARANES WHERE NUMERO=old.NUMERO AND ANNO=old.ANNO;
END^
SET TERM ;^
Espero que te sirva!