I really like Apple Mail's feature of finding dates, times, etc. in emails and allowing you to make a calendar event right then and there, as shown below:

Fine, so I go click the button, and get the calendar popup:

And I edit some things, maybe change the time or add a location. What I want to know is this: how can I now accept the event and add it to the calendar without going back to the mouse? esc closes the window but doesn't add the event. enter does nothing at all, as far as I can tell. I can't even use tab to highlight the Add to Calendar button and then hit enter or [space] as I can in most windows.
Any advice or tips on how to do this?