Middlesex appeared to be headed for a heavy defeat when reduced to 145-7 in the 31st over of their semi-final, chasing 255 to win - Colin Ackermann claiming 3-46 - but Luke Hollman's magnificent, unbeaten 83 steered the home side to a memorable two-wicket win.
Hollman shared in a pivotal 79-run partnership with Tom Helm (40) for the eighth wicket, before Noah Cornwell (1no) hung around as Hollman ticked off the final 31 runs required to clinch victory with eight balls to spare.
- Scorecard: Middlesex beat Durham by two wickets
- Scorecard: Leicestershire beat Notts Outlaws by 13 runs
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Stokes' impact on the semi-final victory was minimal, the former England captain contributing only six runs to Durham's total of 254-7 after electing to bat first.
Will Rhodes hit 80 and Ackerman an unbeaten 71, while Hollman kick-started his superb all-round performance by claiming 3-53 with his leg spin. Zafar Gohar took 2-39, including the key wicket of Stokes, and Naavya Sharma 2-40.
Stokes took 1-40 from nine overs with the ball, claiming the wicket of Michael Atherton's son Joshua de Caires (4) with only his third delivery, but he failed to make further inroads late on to wrestle the match back the visitors' way.
Middlesex will play Leicestershire in the final on Sunday September 20 - live on Sky Sports - after they held on to defend 304 to beat Notts Outlaws by 23 runs in the other semi-final.
Hamza Shaikh, a former England U19s captain, hit 104 from 109 balls - his second hundred in the competition - as Leicestershire posted 303-7 after being inserted, Nick Kelly (53) also hitting fifty as part of a 117-run partnership for the fourth wicket. Dillon Pennington took 3-65.
Leicestershire's 19-year-old pace bowler Alex Green then starred with the ball, taking 4-40 as the Outlaws were bowled out for 280 in reply.
Freddie McCann (64) and Haseeb Hameed (54) gave Notts hope of contesting next month's final on their own ground but the innings lacked the big partnership that might have won it for them, with McCann's run-out a key moment.
