Setting train destinations using combinators.

[mrvn]

It means that when the mine in the far north has ore to deliver that you send a train to THAT mine. Not to the one in the near south that the train automatically picks.

Seeker stations: The only way to do this is to have a unique station per train at each destination. That way you can enable the station corresponding to the train and mine in question. The train will go there and nowhere else.