\def\DFRW{.4\columnwidth}
\def\DFRA{r}

\def\chfootnoterule{\@ifnextchar[ {\@chfootnoterule}{\@chfootnoterule[\DFRA]}}

\def\@chfootnoterule[#1]{\@ifnextchar[ {\@@chfootnoterule[#1]}{\@@chfootnoterule[#1][\DFRW]}}

\def\@@chfootnoterule[#1][#2]{% 
    \if #1l% 
        \lfootnoterule[#2]% 
    \fi
    \if #1r% 
        \rfootnoterule[#2]% 
    \fi% 
}

\def\lfootnoterule[#1]{% 
    \global\def\footnoterule{\kern-3\p@\hrule width #1\kern 2.6\p@}% 
}

\def\rfootnoterule[#1]{% 
    \global\def\footnoterule{% 
        \hbox to \columnwidth{\beginR \vbox{\kern -3\p@\hrule width #1 \kern 2.6\p@}\hfil\endR}% 
    }% 
}