How to implement user attendance tracking parse.com ios

I've developed an ios app using Parse.com backend, My app uses ibeacons for locations linked to a parse class timetable for events in said location.

I'm finding it difficult to implement a way to log users attendance once they enter an ibecaon region (a room) and update parse, which in turn will save a list of users who have attended a timetabled event.

I've seen similar solutions to what I want to do but they all are using personal servers, does anyone have any ideas as to how to solve this.