[docbook-apps] XSLT/CSS border style specifications

[Xmplar]

How does one control the specifications for the various border styles 
for tables, etc. I know how to select the line styles - solid, dashed, 
double, groove, etc - but can the specific metrics for each of these be 
defined? I want to modify the line widths and spacing between lines for 
the 'double' style. (I can specify the overall width of line, but is 
there any finer metrics?) I can't find anything in the XSLT 
specification, apart from the fact that CSS properties apply. nor is 
there anything in the DB stylesheets. I'd like to know if this is 
possible for FO and HTML output.
Thanks,
--
*Dave Gardiner*