%n and %N in NZBPlay not working

[LtChambers]

I'm trying to use these substitutions as described in https://www.altbinz.net/forum/index.php?topic=1390.0
but they're not working for me. My path in NZB Play is:
http://localhost:8042/xbmcCmds/xbmcHttp?command=PlayFile&parameter=%n

I've tried various things after the parameter= part and my browser always comes up with no substitution done (either %n or %N).

This is in version 0.31.3 on Windows 7 x64.