Tikz:矢印の途中に対して矢印したい

\begin{tikzpicture}
\node (A)  {A};
\node (B) [right=of A] {B};
\node (C) [right=of B] {C};
\path (A) edge[->] (B) % simple edges
(B) edge[->] (C);
\draw [->]
($ (B.east) + (4mm,0) $)
-- ++(0,-.5)
-| ($ (B.west) - (4mm,0) $);
\end{tikzpicture}
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