Hi Tracey!
The
GNAS rules of shooting, containing details of all the rounds, can be downloaded from here:
http://www.gnas.org/target/aboutus.cfm
A Western is 4 dozen arrows at 60 yards and 4 dozen arrows at 50 yards, on a 122cm face (the same size we use at Phoenix Bowmen). That might sound a bit daunting, but you and Guy have been shooting so well that I reckon you'll do OK.
Good luck at the shoot!
Tim