Multiselect
There is already a drop_down() method, but a drop_down_multiselect() needs to be added to create a select field that you are able to select more than one option. Similar to the open() method in FB, drop_down() and drop_down_multiselect() can be combined into one method or split into two different methods.
I know @stickgrinder is making some big changes right now and if he doesn't make this change then I can.
ill try to implement this when i retrofit formbuilder to use more of the CI form helper methods.
Uhmmm... I think I fell into a pitfall here: I thought no multiple-select dropdown was possible, so I simply redirected all calls to add_dropdown_field() which selected values was an array to add_multiselect_field(). I have to correct this! :|