That is really your best bet, although I suspect that you are going to have very patchy reception and not be able to maintain a sold connection to the repeaters from the actual end computers. I have personally set up a few long range 10mb connections (over a mile or more) with commercial equipment, but it gets very expensive, very quickly. I used to work a great deal with a company called otc wireless that sold 24db access points and bridges for less than 500 a side, but from a quick glance, it doesn't look like they are around anymore. There are some of their products floating around at a few resellers so if you get some time to search, you might be able to beat these prices: http://www.capitolautomation.com/otc_order.htm

It's not going to be an easy task any way you look at it and will require a lot of trial and error. If you have any other specific questions, feel free to pm me as I don't frequent the board here as much as I used to.