I tried this just a few minutes ago for my server.. I found it was MUCH MUCH easier to make your moderator group teh admin group.. and then all groups higher than them just inherit the admin group. That way when the script performs the IsAdmin check, it'll allow them.
Just go into your groups.txt file and only allow the command you want to have moderators do... make sure you put the rest in superadmin group because it inherits the admin group and if you just go removing thigns from admin, you'll find you wont have them on superadmin either.