I may be using this incorrectly; but I noticed that the checkbox form helper doesn't update id you UNCHECK something. It seems that if the checkbox is unchecked at POST no data is submitted. So a previously checked and submitted item can't be unchecked at a later time using the same form. I can't seem to figure out how to enact an update using the available parameters. Also, the PHP documentor for C5 docs is hard to use because the parameters are not described--they're only listed.