Horn hopes his players channel the hurt from losing 8-1 to Hibs last weekend into their away tie at Kilsyth Rangers.
Reflecting on the defeat to Neil Lennon’s side, Horn said: “I think we are better than what we showed, every goal we conceded was avoidable. It’s not like us and I think the occasion had a lot to do with it.
“We let some people down. I will look back on it and say it was a fantastic achievement, but the regret was we didn’t make more of a game of it.
“I’m looking for a reaction from them, because if they have hurt as much as I have this week, then I’m sure we will get a reaction and we’ll be up for it.”
Winning the Junior Cup would ensure their entry for the William Hill Scottish Cup next season, although the former Berwick Rangers assistant hasn’t given up hope of retaining their Super League crown despite table toppers Kelty Hearts holding a 17-point lead.
Horn continued: “If we can string a couple of results like Kelty have done, then there’s no reason why we can’t go and challenge.
“Saturday is massive, it’s a way of getting back into the big Scottish Cup, but it’s a really difficult tie against Kilsyth who are going well.
“It can be physical, intimidating and they are aggressive. It’s going to be all of that and the players have got to be ready for it and expect it. With what we’ve achieved as well, people are dying to beat us and dying to get at us and knock us down.”
Horn hopes to strengthen his squad for the second half of the season with two additions in the next week, although two of his players are expected to depart.
Elsewhere, Musselburgh Athletic travel to Kirkintilloch to take on West Super League leaders Rob Roy.