how to define rehersal marks globally?

[Ole Schmidt]

Hi,

When I have a score, how can I define rehersal marks globally (instead of in 
every voice) so that they appear in every other voice, when I print it out  
(like below)?

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
global= {
  \time 4/4
  \key c \major
}

violinOne = \new Voice \relative c'' {
  \set Staff.instrumentName = #"Violin 1 "
\mark \default  
  c2 d \mark \default
  e1

  \bar "|."
}

violinTwo = \new Voice \relative c'' {
  \set Staff.instrumentName = #"Violin 2 "

  g2 f
  e1

  \bar "|."
}

viola = \new Voice \relative c' {
  \set Staff.instrumentName = #"Viola "
  \clef alto

  e2 d
  c1

  \bar "|."
}

cello = \new Voice \relative c' {
  \set Staff.instrumentName = #"Cello "
  \clef bass

  c2 b
  a1

  \bar "|."
}

\score {
%  \new StaffGroup <<
%    \new Staff << \global \violinOne >>
%    \new Staff << \global \violinTwo >>
    \new Staff << \global \viola >>
%    \new Staff << \global \cello >>
%  >>
  \layout { }
  \midi { }
}


thanks,  ole