radio button with multiple columns

Hello,

I have a normal has_many :through setup that i need to setup with checkboxes and looking for the best approach.

user
has_many :entries
has_many :contests, :through => :entries

contest

has_many :entries

entry
belongs_to contest
belongs_to user

entry - ID, USER_ID, CONTEST_ID, RANDOM_NUMBER

how would i setup a checkbox/radio button so that i can easily submit to the entry model for each user_id/contest_id/random_number value ?

Thanks
Adam