Controlling which switches to touch is done as Leo says, using triggers, path rules, and specific track marks to keep the AI away from other tracks. There's one thing that might help too if this is taking place in a tight location such as a yard.
The default distance is 20 meters, or roughly 78 feet from the train to the switch. For places where you need to move the lever even with the AI close, set the trigger radius to less than 20 meters. I set mine in my yards to about 2 meters, or roughly 6-feet from the loco or train to the switch. This allows me to switch cars and run right up to the points before setting the junction, making the switching process more realistic.
You can adjust the default 20 meter radius by going to the same panel where you find your track marks. Click on advanced, and you'll see trigger radius. Get the radius of your junction lever (switch), and set that to whatever value you want to use. Repeat on every junction you wish to configure.
John
Any suggestion 