[Tex/LaTex] Framed boxed text with “continued” text on page break

Question

I need to write a boxed text as like as:

Currently, I am using

\documentclass{book}
\usepackage{framed}
\begin{document}

\begin{framed}
\section{Box 15...}
...
\end{framed}

\end{document}

Please advise.

Answer 1

Based on egregs answer to "Breakable vboxes" I coded the following environment. It collects its vertical input and then breaks it using plainTeX's internal breaking mechanism (\vsplit) and places both part in an \fbox. This will not work for large material which break across three pages, but this feature could be added.

\documentclass{article}

\usepackage{blindtext}% just for example text

\newbox\totalbox
\newbox\partialbox
\newdimen\partialboxdim

\newenvironment{continueframe}{%
    \advance\linewidth-2\fboxsep
    \advance\linewidth-2\fboxrule
    \hsize=\linewidth
    \partialboxdim=\dimexpr\pagegoal-\pagetotal-\pageshrink-6pt-\baselineskip\relax
    \setbox\totalbox=\vbox\bgroup\begingroup
}{%
    \endgraf\endgroup\egroup
    \setbox\partialbox=\vsplit\totalbox to\partialboxdim
    \par\smallskip
    \hbox{\fbox{\vbox{\unvbox\partialbox}}}\nopagebreak
    \par\smallskip\mbox{}\hfill\textbf{Continued on next page}\par\pagebreak%
    \hbox{\fbox{\vbox{\noindent\textbf{Contuined from last page}\par\smallskip\unvbox\totalbox}}}%
    \par\medskip
}

\begin{document}

\blindtext
\blindtext
\blindtext

\begin{continueframe}
\blindtext
\blindtext
\blindtext
\end{continueframe}

\blindtext
\blindtext
\blindtext


\end{document}