I'm trying to get the booking engines to give me an advance ticket for a specific service (which I think exists), however it involves two via points. Do any online booking services let you include two via. stations? (For reference, I'm looking to do Cambridge to Edinburgh, via. King's Cross and Glasgow Central on a 1st Class Advance - this is possible later in the day, but it is trying to send me via Tottenham Hale when I look for this particular time of day putting only via GLC).