Average cost per square foot to build a house in Missoula Montana?

Average cost calculations I've used in the past are, $70 ft plus $1000 per outside corner per floor. So a 30x30 house (breadbox or square) that has 2 floors is 1800 ft. 1800 x $70 + 8 x $1000 = $132,000. There are so many things to consider though, and I'm not refering to furnishings those are obvious. Things like current ecomic state is a huge factor, the harder things are, the cheaper labor you'll be able to find. Also, whether you general it yourself and also current material costs.