Greek Text (babel) and English Code Text (listings): Problem

I use the babel package in order to write in greek with font “kerkis”.

I want to add code in english (“courier new” font) to my latex document but I get some difficulties.

Can anybody help me, please.
Thank you in advance.

documentclass[12pt]{article}
usepackage[english,greek]{babel}
usepackage[utf8x]{inputenc}
usepackage{graphicx}
usepackage{fancybox}
usepackage{verbatim}
usepackage{courier}
usepackage{kerkis}
usepackage{float}
usepackage{geometry}
usepackage{fancyhdr}
usepackage{titlesec}
usepackage{tocloft}
usepackage{hyperref}
usepackage{afterpage}
usepackage{color}   
usepackage{listings}

renewcommand{lstlistingname}{Κώδικας}

lstset{ 
%matlab
  backgroundcolor=color{white},  
  basicstyle=normalsize,    % COURIER NEW?     
  commentstyle=color{green},    % comment style
  escapeinside={%*}{*)},        
  extendedchars=true,            
  frame=single,                           
  keywordstyle=color{blue},       % keyword style
  numbers=left,                  
  numbersep=5pt,                  
  numberstyle=normalsizecolor{black}, 
  rulecolor=color{black},        
  stepnumber=1,                   
  stringstyle=color{magenta},     % string style
} 

begin{document}

selectlanguage{greek}
Ελληνικά: textlatin{this word means greek}

selectlanguage{english}
Now I write in english

selectlanguage{greek}
Ελληνικά

%selectlanguage{english}???

begin{lstlisting}
{
% Entropy
E = 0;
for i = 1:J
    if p(i) ~= 0
        E = E + p(i)*log2(1/p(i));
    end
end
}
end{lstlisting}

end{document}