Get / Set Composite Type Fields within triggers

CREATE TYPE info_base AS

   (by text,

    at timestamp without time zone);

I want to use it as the data type of created, modified and deleted fields. I already know hot to index, update and select a sub-field like

CREATE INDEX ix_created_by ON xxx.yyy ((created).by);

UPDATE xxx.yyy SET created.by = 'user';

select * from xxx.yyy where (created).by = 'that user';

My problem is inside triggers: How can I set or get type field values for NEW or OLD? (I need it to check users permissions at row level, etc.)

I tried NEW.((created).by), NEW.(created.by),  NEW.created.by and nothing works...

Could you help me please?

Thanks in advance.

Martin