[web2py] Organizing checkboxes to appear in a 3 column layout

[Andrew Evans]

Hello I have the following field

Field('genre',requires=IS_IN_DB(db,db.genre.id, '%(title)s',
multiple=True), widget=SQLFORM.widgets.checkboxes.widget),

I am trying to figure out how to layout the checkboxes so there in a 3
column grid

Any ideas

*cheers