Goals from Lee Novak and Daniel Ward earned the hosts three points, setting up a showdown with MK Dons who lost to Walsall, giving Grayson's side the advantage of a home tie in the League One play-off semi-final second leg.
The Terriers boss won promotion with Blackpool and Leeds and now wants to complete a treble.
Grayson, who replaced Lee Clark in February, said: "I came here with the objective of promotion and automatic didn't happen for us so we have two games to get to Wembley and finish off what Lee started.
"I wasn't too bothered about where we finished. I have been involved in the play-offs as both a player and a manager and had different results, so there's no real advantage.
"We need to go to MK Dons and get a result and then come back and finish the job at the Galpharm Stadium."
The first leg is at stadium:mk this Saturday (kick-off 12.30pm), with the second leg at the Galpharm on Tuesday, May 15.