por uma logica errada minha, fiz com que me acompanhassem. na realidade, o SQL nao compreende a tabela UPDATED, e sim a INSERTED e DELETED.
CREATE TRIGGER [FCFO_UPDATE]
ON [dbo].[TMOVCOMPL]
after UPDATE
AS
begin
UPDATE FCFOCOMPL
SET CLASSIFICA =
(SELECT (((sum(cast(m.CAMPO1 as numeric(10,2)))/count(*)) +
(sum(cast(m.CAMPO2 as numeric(10,2)))/count(*))+
(sum(cast(m.CAMPO3 as numeric(10,2)))/count(*)))) Valor
from tmovcompl m (nolock)
where m.CAMPO1 is not null and m.CAMPO2 is not null and m.CAMPO3 is not null
and m.idmov in ( select distinct idmov from tmov (nolock)
where codcfo = (select codcfo from INSERTED tmov)) )
where codcfo = (select codcfo from INSERTED tmov)
and codcoligada = (select top 1 codcoligada from INSERTED tmov)
end
Poderia ate ter outra maneira, mas essa ja resolveu.