Diamonds and the Saints, who finished fifth and fourth respectively in the final Evo-Stik Southern League Division One Central table, will battle it out for a place in the Premier Division at ProEdge Westwood Road.
While St Ives were winning a penalty shoot-out at Egham Town, Diamonds claimed a superb 2-1 success at Royston Town, who had finished the regular season as runners-up.
Jack Bowen put Andy Peaks’ side in front in the first half before Dolman slotted home what proved to be the winner from the penalty spot with 10 minutes remaining.
The performance was much more like it from Diamonds, who struggled for form in the latter stages of the season while booking their play-off place.
And while captain Dolman was delighted with their efforts at Garden Walk, he is well aware that the job is only half-done.
“It’s a great feeling, especially after the last couple of months where we haven’t really been at it as a squad,” the Diamonds skipper said.
“To get the victory was a phenomenal performance and we were delighted.
“But nothing is done yet, we have got a big game on Monday and if we play like that we will beat any side in this league.
“The aim at the start was to be in the play-offs and we achieved that.
“There was no pressure on us on Tuesday but I dare say there will be a bit now to go all the way.
“I think we can deal with it. We have shown some character in the last couple of weeks to get into the play-offs and we now feel we are back at the level we are capable of.
“Now we have to make sure we stay there for Monday.”
Dolman, meanwhile, felt Diamonds got things just about spot-on as they sealed that deserved win on Tuesday night.
A high-pressing game proved too much for a Royston side who had claimed two wins over Andy Peaks’ team during the regular season.
“We gave them too much possession in the league game at their ground and in the second half of the one on our pitch,” Dolman added.
“We had to work hard and press the ball high, which is what we did.
“We felt that if we stopped their midfielders from playing then we would stop them completely and I thought we did that very well.
“Our front six were magnificent in their pressing and they gave us the base to build on.
“We could have been two or three up but we went into half-time in front and we pushed on from there instead of sitting back.
“We got the penalty and I’ve stuck that away. It was disappointing to concede late on and put ourselves under pressure but we held on for a great win.”