So, I created a custom list named "Events" and one named "attendees" for an event-management-solution (lets call it attendee training) in a site-collection at my SP2010 Server.
My Problem: I want to create a "register" custom-action (ribbon) for every event in the DispForm of the Events-List, so attendees could register (= add an entry to the attendee list with username (loginName()) and event id) with a click on the button. The Ribbon should show only in this listform, not for every custom list - listform in the site collection.
So far so good, I found this question here: Show custom action in ribbon for only one list and it seems logical to me.
My 'real' Problem (apart from not exactly knowing how to create the ribbon in VS2010, but I think I can figure that out): I want to check if the user is already registered for the event (= into the attendees list), and if he/she is registered, there should not be the "register" action, instead it should appear an "unregister" action.
So now I have no idea how to change the custom ribbon depending on this scenario and hope you could help me.
Best regards, Dominik