Setting the font of SIunits package to sans serif?

[Angus Leeming]

I need some LaTeX guru help ;-)

The attached LaTeX file produces output in which the x-axis label of
the graph is defined as
    Volume (\milli\meter$^3$)

The image is generated by XFig, so I've overridden the definition of
\SetFigFont by adding this to my preamble:

%% Preempt the definition of \SetFigFont in the 
%% xfig-generated pstex_t files.
\gdef\SetFigFont#1#2#3#4#5{%
   [EMAIL PROTECTED]
 \fontfamily{\sfdefault}\fontseries{\mddefault}\fontshape{\updefault}%
   \selectfont}%

That works perfectly, giving me sans-serif labels. Unfortunately, the
"mm^3" bit remains obstinately in a serif font. I've tried adding

\renewcommand{\familydefault}{\sfdefault}

to the preamble. No joy.

I guess that my question comes in two parts:
1. How to specify the font for \milli\meter. Ideally only in the
figures.
2. How to specify the font for ^3.

Regards,
Angus



%% LyX 1.3 created this file.  For more info, see http://www.lyx.org/.
%% Do not edit unless you really know what you are doing.
\documentclass[english]{article}
\usepackage[T1]{fontenc}
\usepackage[latin1]{inputenc}
\usepackage{a4wide}
\usepackage{amsmath}
\usepackage{graphicx}
\usepackage{amssymb}

\usepackage{color}
\usepackage{lmodern}
\usepackage[amssymb]{SIunits}

\renewcommand{\familydefault}{\sfdefault}

%% Preempt the definition of \SetFigFont in the 
%% xfig-generated pstex_t files.
\gdef\SetFigFont#1#2#3#4#5{%
   [EMAIL PROTECTED]
   \fontfamily{\sfdefault}\fontseries{\mddefault}\fontshape{\updefault}%
   \selectfont}%

%% work around LyX bug
%% (LyX swallows \protect in math macros.)
\newcommand{\myprotect}{\protect}

\usepackage{babel}
\makeatother
\begin{document}
%
\begin{figure}
\begin{center}\begin{picture}(0,0)\includegraphics{trial_img.eps}\end{picture}\input{trial_img.pstex_t}\end{center}


\caption{A summation of \citeauthor{Mercer:etal91}'s ventilatory unit volume
distribution data.}
\end{figure}

\end{document}

trial_img.eps
Description: image/eps

\setlength{\unitlength}{3947sp}%
%
\begingroup\makeatletter\ifx\SetFigFont\undefined%
\gdef\SetFigFont#1#2#3#4#5{%
  [EMAIL PROTECTED]
  \fontfamily{#3}\fontseries{#4}\fontshape{#5}%
  \selectfont}%
\fi\endgroup%
\begin{picture}(5884,3579)(1272,-4012)
\put(1838,-3523){\makebox(0,0)[rb]{\smash{{\SetFigFont{10}{12.0}{\familydefault}{\mddefault}{\updefault}
 0}}}}
\put(1838,-3031){\makebox(0,0)[rb]{\smash{{\SetFigFont{10}{12.0}{\familydefault}{\mddefault}{\updefault}
 0.05}}}}
\put(1838,-2540){\makebox(0,0)[rb]{\smash{{\SetFigFont{10}{12.0}{\familydefault}{\mddefault}{\updefault}
 0.1}}}}
\put(1838,-2048){\makebox(0,0)[rb]{\smash{{\SetFigFont{10}{12.0}{\familydefault}{\mddefault}{\updefault}
 0.15}}}}
\put(1838,-1556){\makebox(0,0)[rb]{\smash{{\SetFigFont{10}{12.0}{\familydefault}{\mddefault}{\updefault}
 0.2}}}}
\put(1838,-1065){\makebox(0,0)[rb]{\smash{{\SetFigFont{10}{12.0}{\familydefault}{\mddefault}{\updefault}
 0.25}}}}
\put(1838,-573){\makebox(0,0)[rb]{\smash{{\SetFigFont{10}{12.0}{\familydefault}{\mddefault}{\updefault}
 0.3}}}}
\put(1913,-3648){\makebox(0,0)[b]{\smash{{\SetFigFont{10}{12.0}{\familydefault}{\mddefault}{\updefault}
 0}}}}
\put(2638,-3648){\makebox(0,0)[b]{\smash{{\SetFigFont{10}{12.0}{\familydefault}{\mddefault}{\updefault}
 0.5}}}}
\put(3363,-3648){\makebox(0,0)[b]{\smash{{\SetFigFont{10}{12.0}{\familydefault}{\mddefault}{\updefault}
 1}}}}
\put(4088,-3648){\makebox(0,0)[b]{\smash{{\SetFigFont{10}{12.0}{\familydefault}{\mddefault}{\updefault}
 1.5}}}}
\put(4813,-3648){\makebox(0,0)[b]{\smash{{\SetFigFont{10}{12.0}{\familydefault}{\mddefault}{\updefault}
 2}}}}
\put(5538,-3648){\makebox(0,0)[b]{\smash{{\SetFigFont{10}{12.0}{\familydefault}{\mddefault}{\updefault}
 2.5}}}}
\put(6263,-3648){\makebox(0,0)[b]{\smash{{\SetFigFont{10}{12.0}{\familydefault}{\mddefault}{\updefault}
 3}}}}
\put(6988,-3648){\makebox(0,0)[b]{\smash{{\SetFigFont{10}{12.0}{\familydefault}{\mddefault}{\updefault}
 3.5}}}}
\put(1387,-1986){\rotatebox{90.0}{\makebox(0,0)[b]{\smash{{\SetFigFont{10}{12.0}{\familydefault}{\mddefault}{\updefault}Number
 of ventilatory units (\%)}}}}}
\put(4450,-3960){\makebox(0,0)[b]{\smash{{\SetFigFont{10}{12.0}{\familydefault}{\mddefault}{\updefault}Volume
 (\milli\meter$^3$)}}}}
\put(6388,-741){\makebox(0,0)[rb]{\smash{{\SetFigFont{10}{12.0}{\familydefault}{\mddefault}{\updefault}raw
 data}}}}
\put(6388,-928){\makebox(0,0)[rb]{\smash{{\SetFigFont{10}{12.0}{\familydefault}{\mddefault}{\updefault}log-normal
 distribution}}}}
\end{picture}%