How to automatically add text immediately after \begin{document}

I attempted to redefine the document environment as follows, but get a complaint that:

LaTeX Error: \begin{MYdocument} on input line 13 ended by \end{document}.

\documentclass[12pt]{article}
\newtoks{\SpecialText}
\SpecialText={Text to be printed after begin document}

\newenvironment{MYdocument}{%
\begin{document}{}
Note: \the\SpecialText
}{%
\end{document}
}

\begin{MYdocument}
... file contents ...
\end{MYdocument}

I want this to produce the following output

Note: Text to be printed after begin document

... file contents ...

If I could do this by just slightly modifying the environment that would be preferable so that I could just use \begin{document} ... \end{document}.

-
I tried to make the title of your question clearer by adding the word "text" - is that OK? – Hendrik Vogt Mar 24 '11 at 9:48
The latex-general tag (and also latex3) is for questions about LaTeX and the LaTeX project in general. A good example is Difference between LaTeX, LaTeX2e, LaTeX3?. Your question is about a specific task and therefore should not be tagged with it. – Martin Scharrer Mar 24 '11 at 9:56