Have a look at
this thread, which is a more specific case than what you want, but should get you started.
For instance to check for fold to all-in, just use this:
sum(if[holdem_hand_player_statistics.enum_face_allin='P' AND
holdem_hand_player_statistics.enum_face_allin_action='F', 1, 0])
Tutorial - Custom Reports and StatisticsHave a go at building your stat and if you get stuck post back and we'll help you finish it off.