PL/SQL :: Get Columns Name And Value Dynamically From Trigger

I have to audit some table to log all modifications (inserts, updates, deletes). I wrote the following trigger (works as expected) : 

-- Trigger for DOCUMENT table audit
CREATE OR REPLACE TRIGGER TAUDIT_IUD_DOCUMENT
AFTER INSERT OR UPDATE OR DELETE ON DOCUMENT
FOR EACH ROW
DECLARE
l_user VARCHAR2(64);
[code].........   

Is there any way I can improve this ?I mean getting columns name and value (:NEW and :OLD) dynamically, instead of specifying them one by one (the trigger will have to be updated in case a new column is added). Something like this : 

FOR i in 1..DOCUMENT.COLUMN_COUNT LOOP
l_row := l_row || DOCUMENT.COLUMN_NAME(i) || :NEW.COLUMN_VALUE(i) || l_separator;
END LOOP;