Hi Seth,
I ended up doing what Barry suggested: wiring the sawmill to a MTH AIU port and controlling it with my DCS handheld. Then I removed the Lionel Powermaster from the layout and went to the expense of converting my TMCC engines to MTH DCS. Since I assume you have no Lionel Powermaster this should be an easy solution. Just don't connect a Lionel Powermaster to your layout.
Hope this helps.
Tom