i have no experience, and i'm newbie, but based on
http://wiki.nginx.org/NginxHttpUpstreamModule

if your configuration in i don't know where:
upstream main {
       server localhost:8181;
}
upstream bs {
       server localhost:8282;
}

i guess that you should make 2 file in sites-available containing:
server {
       listen                  80;
       server_name     site.com www.site.com;
       location / {
           proxy_pass http://main
       }
}
and:
server {
       listen                  80;
       server_name     bs.site.com;
       location / {
           proxy_pass http://bs
       }
}

maybe ^^, i don't know yet, would you like to try it?

>
> Please help, I'm on the edge of killing myself. :-)
>
> --
> Pavel
>
i will pray for you ^^
Regards,
GB