iChat server authentication via two seperate AD domains?

I am setting up an iChat server for my school district, but we are in the (slow) process of migrating to an entirely new domain - this puts me in the awkward position of trying to get my iChat server to accept users from two different domains. I've bound my OS X server to one domain and that works great - all my AD users have an iChat account, but I can't figure out how to bring in the second domain. I though I might be able to use the LDApv3 plugin to bring in the second domain, but maybe I'm doing something wrong... I'm entering the IP address of the DC for the second domain, it comes up and auto-selects the AD Server template with the dc= stuff autoentered, but I can't click the Continue button to go any further, and i don't see any option to enter an AD username/password to get the AD info... Guess I should ask: first, is this even possible? and second, how do I do it if it is? Thanks for any advice offered Cheers Jeff