I'm looking for a mod or a way to use a chat channel that will allow a main guild and an alt guild to communicate between the two guilds.  You maybe saying just use Alliance Chat.  Well, yes that works to a degree but the Alliance has more than just those two guilds in it.  This would be used to communicate between the main guild and alt guild without having to have to talk to everyone in alliance chat when you only need to discuss things between the main and alt guild.

have you tried to create a new chat channel? i think that could solve your problem. I think the command is something like "/chan create nameOfChannel", and then just "/chan join nameOfChannel".