\setbeamertemplate{navigation symbols}{}
\setbeamercolor{frametitle}{fg=black}
\setbeamercolor{title}{fg=black}

\usepackage[absolute,overlay]{textpos} % [showboxes]
\newcommand{\myvideobox}{
  \begin{textblock*}{53pt}(403pt,0pt)
    \begin{beamercolorbox}[wd=52.5pt,ht=29pt]{coloredboxstuff}
    \end{beamercolorbox}
  \end{textblock*}
}
\newcommand{\whateverbox}{\myvideobox}
\setbeamercolor{coloredboxstuff}{fg=black,bg=white!95!black}
\addtobeamertemplate{headline}{}{\whateverbox}

\newcommand{\yesbox}{\renewcommand{\whateverbox}{\myvideobox}}  % execute **before** \begin{slide}
\newcommand{\nobox}{\renewcommand{\whateverbox}{}}              % execute **before** \begin{slide}
\nobox
