Okay, just to update everyone and for others that might search this mail-listing:

I have finally gotten it, using the code below in the authorize section I can send host authentication to multiple proxies based on domain name

    if ( User-Name =~ /^host\//i ) {
        if ( User-Name =~ /\\.first\\.domain$/i ) {
            update control {
                Proxy-To-Realm := "first.domain"
            }
        }
        if ( User-Name =~ /\\.second\\.domain$/i ) {
            update control {
                Proxy-To-Realm := "second.domain"
            }
        }
        if ( User-Name =~ /\\.first\\.domain$/i ) {
            update control {
                Proxy-To-Realm := "third.domain"
            }
        }
    }

For whatever reason I had to use 2 backslashes in front of the period in the domain names?? But anyway, this part of the project is working.

Thanks for all the help!
Bob