First of all - thanks for the reply
Perhaps my reference to a file name was a little misleading. The content which requires specific tray is within an ERP system, so the user is not printing a file (per se) or (MS) Office application, so I don't think a print shortcut of that nature is an option. The ERP application in also not exclusively for the special tray printing, only specific records.
We are also running MFP-s by Kyocera which maintain Printing Logs, which actually show the file name or at least the content name which is being printed. I assumed that although I can't see the printing logs of that nature on LaserJets, this data is still forwarded internally and the printer can ID the content that should be sent to another tray.