R help - Jun 2009 - Modifying Sweave.sty to allow escapes with fancyvrb package in LaTeX

Dear Colleagues:

In an attempt to have things like # See page \pageref{this} inside 
comments in R code chunks I have modified Sweave.sty as below.  I have 
followed fancyvrb's manual with regard to the use of the commandchars 
argument.  But when compiling with LaTeX (using attached test file) I 
get a LaTeX error

(/usr/share/texmf-texlive/tex/latex/ae/t1aett.fd)
! Missing \endcsname inserted.
<to be read again>
                    \global
l.25  } else y <- 4

The line in question is 
\DefineVerbatimEnvironment{Sinput}{Verbatim}{formatcom=\lstset{fancyvrb=true},commandchars=\\\{\}}

Can anyone give me a pointer to how to properly change Sweave.sty to 
allow it to use fancyvrb in this way?  I am following the model in 
SweaveListingUtils for having Sweave use the listings package to do 
pretty-printing.

Thanks very much
Frank


Sweavel.sty:

\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{Sweavel}{}

\RequirePackage{listings,ifthen,graphicx,fancyvrb,relsize}
\RequirePackage{ifthen}
\newboolean{Sweave at gin}
\setboolean{Sweave at gin}{true}
\newboolean{Sweave at ae}
\setboolean{Sweave at ae}{true}

\DeclareOption{nogin}{\setboolean{Sweave at gin}{false}}
\DeclareOption{noae}{\setboolean{Sweave at ae}{false}}
\ProcessOptions

\IfFileExists{upquote.sty}{\RequirePackage{upquote}}{}

\ifthenelse{\boolean{Sweave at gin}}{\setkeys{Gin}{width=0.8\textwidth}}{}%
\ifthenelse{\boolean{Sweave at ae}}{%
   \RequirePackage[T1]{fontenc}
   \RequirePackage{ae}
}{}%

%\DefineVerbatimEnvironment{Sinput}{Verbatim}{fontshape=sl}
\DefineVerbatimEnvironment{Sinput}{Verbatim}{formatcom=\lstset{fancyvrb=true},commandchars=\\\{\}}
\DefineVerbatimEnvironment{Soutput}{Verbatim}{}
\DefineVerbatimEnvironment{Scode}{Verbatim}{fontshape=sl}

\newenvironment{Schunk}{}{}

\newcommand{\Sconcordance}[1]{%
   \ifx\pdfoutput\undefined%
   \csname newcount\endcsname\pdfoutput\fi%
   \ifcase\pdfoutput\special{#1}%
   \else\immediate\pdfobj{#1}\fi}

-- 
Frank E Harrell Jr   Professor and Chair           School of Medicine
                      Department of Biostatistics   Vanderbilt University
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