Case statement for other info

Hi guys, I really need your help on a case please.
 
I need to retrieve info from a column that contains a name instead of a numeric value such as " CASE WHEN EventCodes = 'Registered' THEN COUNT(EventCodes) END AS 'Tournament Registrations'

How can I find out also the number of people that haven't registered? I can't do a "WHERE NOT" as I also need to obtain info just from one month so I need to populate the WHERE clause with WHERE Date BETWEEN this AND this.

Any help would be appreciated thanks :)