The below should do the trick.
Type: Query
Triggers: onAfterUserUpdate
Access: Everybody
Conditional: [cb_checkbox] Equal To 1
Query:
Code:
UPDATE `#__comprofiler` SET `confirmed` = 0 WHERE `id` = '[user_id]'
I'm not sure if you meant CBs confirmation field or not, but the above adjusts it. The below adjusts "block", which IMO seams the most appropriate.
Code:
UPDATE `#__users` SET `block` = 1 WHERE `id` = '[user_id]'
You could also have a second auto action after this that'll log them out too.