[AUCTeX] Formatting questions

[Siim Sepman]

Greetings!

I can't seem to get the formatting right.
I want the side boarders of the inner boxes exactly overlap with the
borders of the outer box and still overlap in the middle as they do
now.
I also want the upper border of the box containing "aaa aaa..." to
exactly overlap with the surrounding box withouth having to specify
any numerical lengths.

Here's the result so far: http://kom.aau.dk/~ssepman/AAA.png
I've zoomed in with the PostScript viewer to better show the flaws.

Additional questions:
Is there a command, which gives you the length from current position
to the right border of the current box/environment?
Why does \vspace{20mm} have no effect in current context?
Even if we removed \vspace{20mm} command, we'd have the same vertical
gap between the horizontal line and the big box. Why? How to get rid
of it?

[CODE]
\documentclass{article}
\setlength{\parindent}{0pt}
\setlength{\parskip}{0pt}
\setlength{\fboxsep}{0in}
\begin{document}
\framebox[\textwidth]{\hrulefill}
\vspace{20mm}
\framebox[\textwidth]
{%
        \fbox{\begin{minipage}[t]{0.5\textwidth}
                AAA AAA AAA AAA AAA AAA AAA AAA AAA AAA AAA.
        \par
                AAA AAA AAA AAA AAA AAA AAA AAA AAA AAA AAA.
        \end{minipage}}%
%
        \fbox{\begin{minipage}[t]{0.5\textwidth}
                aaa aaa aaa aaa aaa aaa aaa aaa aaa aaa aaa.
        \end{minipage}}%
}%
\end{document}
[/CODE]

Best Regards,
-Siim

-- 
http://kom.aau.dk/~ssepman/