This won't solve your problem, but may give you another idea:
We have a couple installations with about ten TS-480 users each. To help
with the coordination, we created a Google Doc (Drive) spreadsheet. The
advantage of Google Docs is that multiple users can edit and view the doc
at the same time.
The user notes at the top of the sheet that he is using the station. Then the
others know not only that the station is in use, but also know who is using it
and can use the built-in chat function to ask when they can use it.
We also use it for a log, which allows you to track who was using the station at
what time and to do year-end statistics on usage for calculating usage costs if necessary.
We have not had a problem you described below, but to be quite honest, it virtually
never happens because we use this system for coordination.
73,
Mitch DJ0QN / K7DX