If you want to set dates for the new created event before opening the lightbox, you can set dates in the onBeforeLightbox handler.
Check there if it is new event by getState method. scheduler.getState().new_event
To make the event readonly in the lightbox - update the value of ‘readonly’ property in the events object as it described here. To implement it, add select or checkbox control to the lightbox.
after the description is it possible? does it not break anything? I’ve seen your demos and all those samples is the same displaying time period at the bottom.