Sebastian, this came yesterday on usenet comp.text.tex Perhaps you
           could put it up on ftp.tex.ac.uk. Cheers, Michel
----------------------------Original message----------------------------
% ---- start of the style file ----
% hvdashln.sty : h(orizontal and )v(ertical )dash(ed )l(i)n(e).sty
%
%					By nakasima@kuis.kyoto-u.ac.jp
%
% \hdashline is for the horizontal dashed line
% \vdashline is for the vertical one
%
% parameters :
%
% \hdashlinewidth  (w)
% \hdashlinegap    (g)
%
%	w=4pt
%	|---   ---   ---   ---|
%	   g=4pt
%
\newcount\hdl@columns
\let\hdl@mkpream\@mkpream
\def\@mkpream{\hdl@columns\@ne \hdl@mkpream}
\def\@addamp{\if@firstamp\@firstampfalse
   \else\edef\@preamble{\@preamble &}\advance\hdl@columns\@ne\fi}
\def\hdashline{\multispan{\hdl@columns}\unskip
   \vrule\@height\arrayrulewidth\@width\hdashlinewidth
   \hskip.5\hdashlinegap
   \xleaders\hbox{\hskip.5\hdashlinegap
   \vrule\@height\arrayrulewidth\@width\hdashlinewidth
   \hskip.5\hdashlinegap}\hfill
   \hskip.5\hdashlinegap
   \vrule\@height\arrayrulewidth\@width\hdashlinewidth\cr
   \noalign{\vskip-\arrayrulewidth}}
\newdimen\hdashlinewidth \hdashlinewidth4pt %
\newdimen\hdashlinegap \hdashlinegap4pt %
\def\vdashline{\hskip\arraycolsep
   \@tempdima\ht\@arstrutbox \advance\@tempdima\dp\@arstrutbox
   \lower\dp\@arstrutbox\vbox to\@tempdima{
   \hrule\@height.5\hdashlinewidth\@width\arrayrulewidth
   \vskip.5\hdashlinegap
   \xleaders\vbox{\vskip.5\hdashlinegap
   \hrule\@height\hdashlinewidth\@width\arrayrulewidth
     \vskip.5\hdashlinegap}\vfil
   \vskip.5\hdashlinegap
     \hrule\@height.5\hdashlinewidth\@width\arrayrulewidth}%
   \hskip\arraycolsep}
\endinput
% sample
\documentstyle[hvdashln]{article}
\title{Usage of {\tt hvdashln.sty}}
\author{Nakashima}
\date{Nov. 16, 1992}
\hdashlinewidth=2pt \hdashlinegap=2pt
\begin{document}
\maketitle\thispagestyle{empty}
Definitions of horizontal and vertical dashed lines for
{\tt array} and {\tt tabular} environment.
Instead of partial horizontal dashed line by
 the \verb+\cline{2-3}+ by Isozaki,
\verb+\hdashline+ fills the full width.
The proportion of the dashed line is defined by the two
parameters: \verb+\hdashlinewidth=2pt+ and
 \verb+\hdashlinegap=2pt+, where the former defines the
width of the dash and the latter sets their gap.
The default values of these are {\tt 4pt} while
{\tt 2pt} is employed in the examples below.
\medskip
\[
\left[
\begin{array}{c @{\vdashline} cc}
  A & B & C \\
   \hdashline
  D & E & F \\
  G & H & I
\end{array}
\right]
\]
\bigskip
\begin{minipage}[t]{.48\textwidth}
\begin{center}
\begin{tabular}{|c|c|c|} \hline
a & b & c \\ \hline
a & b & c \\ \hline
a & b & c \\ \hline
\end{tabular}
\end{center}
\end{minipage}
\begin{minipage}[t]{.48\textwidth}
\begin{center}
\begin{tabular}{|c @{\vdashline} c|c|} \hdashline
a & b & c \\ \hdashline
a & b & c \\ \hline
a & b & c \\ \hdashline
\end{tabular}
\end{center}
\end{minipage}
\end{document}
% (Mitsuo Hirata)
% (hirata@nssun.te.chiba-u.ac.jp)
% ---- end of the style file ----