set proxy only for some specific pages (and different proxy everytime)

I have foxyproxy but I think that when I put a proxy it works only for all of the pages.
I'd like an add on that puts a different proxy everytime I go to those specific pages... I'd also like to chose the proxies before because some proxies don't work with those pages. Can you help me?

Also, this doens't have to deal with proxy but... do you know a way to make IMACROS run all of the iim files one after the other? I use firefox.

Thank you!