Bobby Gamble (pictured) was the hero for YMCA hitting two sixes in the last over to beat North County and all but seal their Premiership slot later this summer.
It was a fitting end to a dramatic contest which swung one way then the other during the high scoring affair.
Gamble's half century got the Claremont Road side over the line as they chased 276 at Inch - Tim Tector also getting a half century.
Jonathan Andrews and Eddie Richardson scored fifties for County in their 276 for 7 which in the end wasn't enough.
Merrion teenager Peter Forkin had a senior debut to remember as he took a five-wicket haul as the Angelsea Road made it six wins out of six with an emphatic seven wicket win over Leinster to set up a home semi-final in two weeks time.
Phoenix's Matt Lunson went one better taking six wickets in their victory at Railway - Ben Beecroft making 60 as his side raced to victory and moved into second slot ahead of next Sunday's final round of games.
Half centuries from Daya Singh, Joey Carroll and Mark Donegan saw The Hills also made it six of the best as they ended Malahide's long league unbeaten run with a 40 run win at Milverton which gives them the other home draw in the semi-final.
They will most likely face Pembroke, who chased 277 to beat Rush, thanks to a fourth wicket stand of 182 in 30 overs between centurion Theo Lawson 9107) and Shaheen Khan (64).
The loss means it's likely to be a winner takes all clash between Rush and Balbriggan for the fourth Premier slot.
LEINSTER SENIOR LEAGUE CUP
At Milverton, The Hills beat Malahide by 40 runs
The Hills 247/8 (50 overs; J Carroll 62, M Donegan 53, Daya Singh 51, T Rooney-Murphy 40*;M Ford 2-36, P Chase 2-47)
Malahide 203 (38.5 overs; Anish Desai 74, G Ford 54, Arjun Muntha 21; Devender Ranolia 3-34, Daya Singh 3-39)
At Terenure, Terenure lost to Clontarf by 8 wickets
Terenure 133 (42.1 overs; Sidarth Nair 67, D Vaughan 27; Shariful Islam 3-17, M Wright 2-16)
At Rathmines, Leinster lost to Merrion by 7 wickets
Leinster 103 (29.3 overs; Monil Patel 26, G Dellany 24; P Forkin 5-15, J Groom 2-11, T Stanton 2-21)
Merrion 104/3 (18.5 overs; J Anderson 41*, M Sorensen 23*; G Delany 2-48)
At Inch, North County lost to YMCA by 2 wickets
North County 276/7 (50 overs; J Andrews 72, E Richardson 70, N McGovern 40, Y Cook 24; H Tector 3-45, J Parkinson 3-47)
YMCA 281/8 (50 overs; T Tector 53, B Gamble 50*, R Anders 40, J Cassidy 38, F Hand 35; E Richardson 3-44. A Sheridan 3-50)
At Park Avenue, Railway Union lost to Phoenix by 6 wickets)
Railway Union 109 (40.5 overs; Saad Ullah 37, A Stiles 22; M Lunson 6-31, Amish Sidhu 2-14, B White 2-25)
Phoenix 113/4 (16.2 overs; B Beecroft 60, N Pretorius 20*)
At Kenure, Rush lost to Pembroke by 4 wickets
Rush 276/9 (50 overs; N McGuire 73, S Ramnathphur 70, N Rock 48, P Viswanath 39; R Hopkins 4-61, J Balbirnie 3-45)
Pembroke 277/6 (48.5 overs; T Lawson 107, Shaheen Khan 64, D Heverin 28; J Barnes 2-35, J Snyman 2-54)