Ability for members to uncheck one of the classes in the list

Currently the member clicks register on the 1st activity in the list then they will see all the dates. but once you click register that date can not be unclicked when you see the list of Dates. If the member changes their mind they have to go all the way out and scroll to the 1st date in the list they want to register and click register then choose all the dates they want. - it is a lot of steps when the default check mark could just be able to be unchecked