\documentclass{article}
\newcounter{num}
\newenvironment{sample}{\begin{list}{\textbf{Sample \Alph{num}}\hfill}%
   {\usecounter{num} \setlength{\labelwidth}{20mm}
    \setlength{\leftmargin}{22mm} \setlength{\rightmargin}{5mm}
    \setlength{\itemsep}{1ex plus0.5ex minus 0.4ex}
    \setlength{\listparindent}{1em}
    \setlength{\parsep}{0ex plus0.5ex} }}
   {\end{list}}
\begin{document}
The user defined \texttt{sample}-environment of the upper preamble
demontrates the position of the corresponding label and their
left an right margins.  
\begin{sample}
\item with no commercial value.
\item on receipt of the enclosed voucher an amount of 5.00 \$ will be
      paid.
\end{sample}
\end{document}
