Auto http authenticate traffic for a specific site with fiddler

I am trying to figure out how I can get fiddler to autorespond or modify an http authenticate basic response so I don't have to keep entering in the username/password (I have over 200 sub-domains to try that require the credentials and I want to avoid doing each one).

I've tried adding in a autoresponder rule to identify the www-authenticate request with the value of Basic XXXXXXXXXXXX(encode string), but it doesn't seem to work when I am using a browser as a proxy set to fiddler (IE: localhost, port 8888)...

I have also tried adding into custom rules (and setting the "auto authenticate" flags): oSession["X-AutoAuth"] = "domain\username:password"; but that didn't work either.

Anyone know how I can do this? Did I miss something? Is there a better tool to handle this modification and how would I go about it?