[GENERAL] Is this possible in a trigger?

[Fernando]

I want to keep a history of changes on a field in a table.  This will be 
the case in multiple tables.

Can I create a trigger that loops the OLD and NEW values and compares 
the values and if they are different creates a change string as follows:

e.g;

FOR EACH field IN NEW
   IF field.value <> OLD.field.name THEN
      changes := changes
           || field.name
           || ' was: '
           || OLD.field.value
           || ' now is: '
           || field.value
           || '\n\r';
   END IF
END FOR;

Your help is really appreciated.

Thank you.