\documentclass[a4paper]{article}
\makeatletter
\def\afterfi#1\fi{\fi#1}
\let\ORIGaddtocontents\addtocontents
\newcommand*\dontaddtolof[2]{\edef\temp{#1}%
  \ifx\temp\ext@figure\else\afterfi\ORIGaddtocontents{#1}{#2}\fi}
\makeatletter
\newcommand*\ignorelof{\let\addtocontents\dontaddtolof}
\newcommand*\obeylof{\let\addtocontents\ORIGaddtocontents}

\begin{document}
\listoffigures
\begin{figure}\caption{foo}\end{figure}
\ignorelof
\begin{figure}\caption{bar1}\end{figure}
\begin{figure}\caption{bar2}\end{figure}
\obeylof
\begin{figure}\caption{faz}\end{figure}
\end{document}