help with creating an environment

[Artimess]

I would like to create a LyX module for the  environment that I borrowed
from the tex version of memoir book (code e  in blue).  I used Steve Litt's
tutorial to experiment with it (code in green), when I run  I get  two
errors in red.

I would appreciate if you explain to me what I am doing wrong.
Also, It is preferable t have this as module rater than layout how should I
go about doing it as a module?

Many thanks,
Artimess

 ! LaTeX Error: Environment Syntax undefined.

! LaTeX Error: \begin{document} ended by \end{Syntax}.


%%%%% LaTeX syntax
%%%% control space above/below center environment
\newcommand*{\tightcenter}{%
  \topsep=0.25\onelineskip\trivlist \centering\item\relax}
\def\endtightcenter{\endtrivlist}
\newenvironment{syntax}{\begin{tightcenter}
                        \begin{tabular}{|p{0.9\linewidth}|} \hline}%
                       {\hline
                        \end{tabular}
                        \end{tightcenter}}



#% Do not delete the line below; configure depends on this
#  \DeclareLaTeXClass[book]{mybook}

Input stdclass.inc

Preamble
%%%%% LaTeX syntax
%%%% control space above/below center environment
\newcommand*{\tightcenter}{%
  \topsep=0.25\onelineskip\trivlist \centering\item\relax}
\def\endtightcenter{\endtrivlist}
\newenvironment{syntax}{%
                         ~\\
                        \begin{tightcenter}
                        \begin{tabular}{|p{0.9\linewidth}|} \hline}%
                       {\hline
                        \end{tabular}
                        \end{tightcenter}
  ~\\

                         }

EndPreamble

Style Syntax
Style Syntax
  CopyStyle Standard
  LatexType             Environment
  LatexName             Syntax
  LeftMargin        "MMMMMM"
  RightMargin        "MMMMMM"
  Font
    Shape               Italic
  EndFont
End