You will need a pair of columns like this:
actions =
sum( if[holdem_hand_player_detail.amt_bet_ttl / holdem_limit.amt_bb > 25 AND NOT holdem_hand_player_statistics.flg_showdown AND NOT holdem_hand_player_statistics.flg_won_hand, 1, 0 ] )
opportunities =
sum( if[holdem_hand_player_detail.amt_bet_ttl > 25, 1, 0 ] )
For how to build a stat from expressions like these check out the
Tutorial: Custom Reports and Statistics.
Here "actions" counts the number of times the player bet more than 25 BB, didn't go to showdown and didn't win the hand (therefore folded at some point), and "opportunities" counts the number of times they bet more than 25 BB.