Not a mod, a program.
http://code.google.com/p/mlox/wiki/Tes3cmd
And if you're going to use MGE, there are some special steps for set-up. Check the MGE thread.
Like i said in your other post of the http://www.gamesas.com/index.php?/topic/1106724-needed-fixes/page__view__findpost__p__16205222