Visiting striker Jamie Ward's sublime first-half chip looked certain to seal the points for the promotion hopefuls against a confidence-shot Stanley side.
But Chesterfield defender Aaron Downes gifted substitute Proctor the perfect opportunity to level from the penalty spot with 17 minutes remaining.
And D'Sane, the striker fouled in the box by Downes, popped up with just two minutes remaining to grab the three points that dented Chesterfield's promotion charge.
Stanley piled on the pressure in search of redemption, but they weren't creating anything.
And it was only when Proctor, on as sub in the 66th minute, stroked home from 12 yards that they got some real momentum going with the chances to match.
Paul Mullin missed a gilt-edged opportunity just seconds before D'Sane headed home Ian Craney's pinpoint right-wing corner with the clock ticking down.
From the moment Ward latched on to an inch perfect crossfield ball from German left winger Felix Bastiens, on loan from Nottingham Forest, to beat a stranded Ian Dunbavin from all of 25 yards after 17 minutes, an away win looked odds on.
It truly was a goal that deserved to win any game of football from Premier League down to League Two. Players up and down the land will have to go some to prevent this featuring in the goal of the season reckoning.
But Chesterfield just couldn't hold on to continue Accrington's home woes, with their manager, Lee Richardson blasting: "That was not good enough. We have contrived yet again to gift them the game."
Despite Accrington's home woes, their away form is reasonable. If they can somehow manage to use this as a springboard for more home successes, then Christmas in East Lancashire will be far better than it looked like being with 17 minutes of this match remaining.