Hello Boyan, thanks for your reply!
From the solutions you suggested, the one who would fit to our needs would be the KeyDown event. The problem with the second solution is that we don't know when the selection changed, something you informed in the response below, what would make countless calls to our async service for every date selected. The KeyDown event is a good candidate, but we figured out that it just works when we click off the object's 'surface'. If you guys make it fire the event once the KeyDown is pressed over the date, that would be the way to go.
Any possibilities for that?
Once again, thanks for your comprehension.