Highlight one line of a listing at a time in LaTeX

diapo.tex

\documentclass[12pt]{beamer}
\usepackage[spanish]{babel}
\usepackage[utf8]{inputenc}
\usepackage{xcolor}
\usepackage{listings}
\usepackage{palatino}

\usefonttheme{serif}

\lstloadlanguages{fortran}
\lstset{language=fortran,aboveskip=0pt,belowskip=0pt,showlines=true}
\lstdefinestyle{h}{backgroundcolor=\color{orange}}

\newcommand{\emphline}[4]{%
  \lstinputlisting[linerange={#1}]{#4}
  \lstinputlisting[linerange={#2}-{#2},style=h]{#4}
  \lstinputlisting[linerange={#3}]{#4}
}

\begin{document}
  \begin{frame}
    \only<1> {\emphline{1-5} {6} {7-15} {potencia.f95}}
    \only<2> {\emphline{1-6} {7} {8-15} {potencia.f95}}
    \only<3> {\emphline{1-8} {9} {10-15}{potencia.f95}}
    \only<4> {\emphline{1-9} {10}{11-15}{potencia.f95}}
    \only<5> {\emphline{1-10}{11}{12-15}{potencia.f95}}
    \only<6> {\emphline{1-9} {10}{11-15}{potencia.f95}}
    \only<7> {\emphline{1-10}{11}{12-15}{potencia.f95}}
    \only<8> {\emphline{1-9} {10}{11-15}{potencia.f95}}
    \only<9> {\emphline{1-10}{11}{12-15}{potencia.f95}}
    \only<10>{\emphline{1-9} {10}{11-15}{potencia.f95}}
    \only<11>{\emphline{1-13}{14}{15-15}{potencia.f95}}
  \end{frame}
\end{document}

potencia.f95

program potencia
    implicit none
    real :: base, resultado
    integer :: exponente, i

    read *, base
    read *, exponente

    resultado = 1
    do i = 1, exponente
        resultado = resultado * base
    end do

    print *, resultado
end program potencia

Here's how I automated the solution a bit by using a counter:

http://tex.stackexchange.com/questions/64883/counting-lines-and-making-calculations/64888#64888