What you need to use is an enzyme cleaner. I use one by chemspec called enz-all and it does great on these types of stains when used with a good extractor.
now, I understand that you would not want to spend the bucks on the enz-all for one time use, so, how do we find a cheap enzyme cleaner? We go to the local pet store and get some of the pet stain remover, this is a high enzyme and high PH cleaner,, just what you need.
do it like this.
Spray some of the cleaner on the spot and let it set for about 15 minutes. then, with a rented carpet extractor from Giant or where ever you rent them there, mix the cleaner in with the water and do a very slow pull across the stain while putting down the cleaner.
do the whole carpet with this.
Oh, and as an enzyme cleaner works, it breaks down protiens and releases them into the air as a gas, so,, be warned that if you do have any pee in the carpets, you might want to keep the windows open for a couple hours after you do it.
if that fails, get ahold of me and I might be able to come on down over the weekend and help you out.