[web2py] Update, create a log and show an extra field in SQLFORM

[Vinicius Assef]

Hi guys.

I have this model:

db.define_table('parent',
  Field('name', 'string'),
  format='%(name)')
db.define_table('child',
  Field('name', 'string'),
  Field('relation', 'string'),
  Field('parent_id', db.parent),
  format='%(name)s %(relation)s')

I need to develop a feature to change the child's parent and store
this operation in a log table.

I thought about showing a SQLFORM with all these fields and an extra
one, created dynamically, using the same IS_IN_DB() validation like
the db.child.parent_id.
But, how can I do this?

Is there another simpler way to achieve my goal?

Thanks in advance.

--
Vinicius Assef.