The competition, organised by the official supporters club will be launched during Saturday's visit of Rushden and Diamonds.
Fans who register in the Iron Bar beforehand will have their names put into a hat, and three will be drawn out to take part in the competition at half-time.
They will be asked to hit the crossbar from the edge of the penalty area, with the first person to do so taking the cash prize - initially £25 but rising to £100 or more for future games.
If there is no winner, the prize fund will roll over to the following home game.
OSC chairman Andy Brown told Iron-Bru.net: "Fans have been asking us if there's anything we can do at half-time to jazz it up a bit.
"It is a trial run at first, but we're looking for a sponsor for next season to take it on a bit. We hope it'll be a bit of fun, and that it'll really take off."