partcombine for more than two parts?

[Niki Pantelias]

  Hi everyone,

  Does anyone know if it's possible to combine more than two voices with 
\partcombine (or something else :-)?  I'd like to be able to print, say, a 
single staff containing all four trumpet parts so I can easily see the 
chord voicings, and also be able to print the individual parts from the 
same input file.

  thanks!
  -- Niki