Path to midpoint of other path

Question

I would like to end a path at the midpoint of another path. My inclination has been to try and end the path at an offset equal to half the node distance from d.north, but any thing I seem to try will not compile. Here's what I have so far (the end goal being the 'No' path ending at 'HERE' )

\documentclass{article}

\usepackage{tikz}
\usetikzlibrary{shapes,arrows,calc}
\begin{document}
\pagestyle{empty}    

% Define block styles
\tikzstyle{box} = [rectangle, draw]
\tikzstyle{line} = [draw, -latex']

\begin{tikzpicture}[node distance = 3cm, auto]
    % Place nodes
    \node [box] (a) {A};
    \node [box, below of=a] (b) {B};
    \node [box, below of=b] (c) {C};
    \node [box, below of=c] (d) {D};

       % Draw edges
    \path [line] (a) -- (b);
    \path [line] (b) -- (c);
    \path [line] (c) -- node [midway, left] {HERE} (d);

   \path [line] (a.east) --node [above] {No}  +(1,0) |- (d.north);     

\end{tikzpicture}

\end{document}

I've seen some things on path decorations, but I'm really unsure how to use them and not sure that I can end the path on them.

Answer 1

Your code already contains a solution (without calc library): midway!

\documentclass{standalone}
\usepackage{tikz}
\usepackage{tikz}
\usetikzlibrary{shapes,arrows}

\tikzstyle{box} = [rectangle, draw]
\tikzstyle{line} = [draw, -latex']

\begin{document}
\begin{tikzpicture}[node distance = 3cm, auto]
    % Place nodes
    \node [box] (a) {A};
    \node [box, below of=a] (b) {B};
    \node [box, below of=b] (c) {C};
    \node [box, below of=c] (d) {D};

       % Draw edges
    \path [line] (a) -- (b);
    \path [line] (b) -- (c);
    \path [line] (c) -- coordinate[midway](m) (d);

   \path [line] (a.east) --node [above] {No}  +(1,0) |- (m);     
\end{tikzpicture}
\end{document}

Answer 2

Like this? (c)!0.5!(d) means halfway between (c) and (d).

\documentclass{article}

\usepackage{tikz}
\usetikzlibrary{shapes,arrows,calc}
\begin{document}
\pagestyle{empty}    

% Define block styles
\tikzstyle{box} = [rectangle, draw]
\tikzstyle{line} = [draw, -latex']

\begin{tikzpicture}[node distance = 3cm, auto]
    % Place nodes
    \node [box] (a) {A};
    \node [box, below of=a] (b) {B};
    \node [box, below of=b] (c) {C};
    \node [box, below of=c] (d) {D};

       % Draw edges
    \path [line] (a) -- (b);
    \path [line] (b) -- (c);
    \path [line] (c) -- node [midway, left] {HERE} (d);

   \path[line] let \p1 = ( $(c)!0.5!(d) $ ) in (a.east) --node [above] {No}  +(1,0) |- +(0,\y1);     

\end{tikzpicture}

\end{document}