Brown missed Tuesday's 2-1 win over Harrogate Railway with a sore hamstring while Coo limped out of the action early in the second half.
With injuries already depriving Vince of a host of players, the Shay chief could have as few as 14 players to select from.
"We are just not sure whether Cavell or Junior will recover to play," said Vince.
"But it is not looking particularly good at the moment.
"We could end up with one or both, it depends if Alan Russell Cox can work his miracles on them."
Vince was only able to name four subs for Tuesday's game and the only fit member of the squad not to feature was back up keeper Phil Senior.
"These things happen," said Vince. "It appears all doom and gloom on the injury front, but it is part of the game."
Woodley Sports will be playing their fourth game in eight days tomorrow having endured a double header last weekend when they beat Harrogate Railway at home on Saturday before drawing at Newcastle Blue Star 24 hours later.
The Stockport side then went to Clitheroe on Wednesday and had a 3-2 win.
"I imagine they will be confident after a run like that," said Vince. "But we are confident as well. As long as we are on our game tomorrow we will be all right."
Town go into tomorrow's contest hot on the heels of Durham, whose lead at the top of Unibond One North is just a point.
And while Vince knows the importance of building momentum after Tuesday's win, he is looking no further ahead than the Woodley game.
"We have to focus on tomorrow and picking up three points," he said. "We can look no further ahead than that.
"We have to keep the pressure on game by game and be in a position to capitalise on any mistakes our rivals make."
FC Halifax Town (from): Kennedy, Coo, Barras, Sutton, Adams, Hinsley, Allen, Evans, Baker, J Brown, Barnes, Peers, Stott, D Brown, Jemson, Senior.

SUPPORTERS team AFC Halifax bowed out of the IFA National Cup at the quarter final stage, beaten 4-2 at Aberdeen.
Second half goals from Martin Bishop were not enough for AFC Halifax, who are at home to Bury tomorrow (10.30).
Liverpool manager Rafael Benitez has hinted he could walk away from Merseyside if stability is not brought to Anfield.
The Spaniard is yet to sign a new contract with the Reds despite having little more than a year to run on his current deal.
"I must decide on my future in the next two weeks and I want a medium or long-term project," he said.
"I don't want to be working from day to day always hanging on the latest result. I will work where I can develop a project."