How do I create dll in a Matlab 7.9 (R2009b) version?

I have this code:

   function preprocesado(Nombre)
    Carpeta=Nombre;
    if ~isdir(Carpeta)
    errorMensaje = sprintf('Error: La carpeta no existe:\n%s', Carpeta);
    uiwait(warndlg(errorMensaje));
    return;
    end
    filePatron = fullfile(Carpeta, '*.jpg');
    jpegFil = dir(filePatron);
    names = struct2cell(jpegFil);
    names = (names(1,:));
    Mitad=length(jpegFil)/2;
    MitadR=round(Mitad);
    baseFN = jpegFil(MitadR).name;
    fullFN = fullfile(Carpeta, baseFN);
    I=imread(fullFN);
    %Convertir a escala de Grises
    imOrGris=rgb2gray(I);
    %Versión binaria por el método de Otsu
    Ib=graythresh(imOrGris);
    BN = im2bw(imOrGris,Ib);
    %Se aplica una máscara de 25 x 25 pixeles
    Ibmask=medfilt2(BN,[25 25]);
    %Se elige la región ROI
    iROI=roicolor(Ibmask,1);
    imcrop(iROI)

And I want to create dll because I want to use it in Labview, I already have tried but it didn't function. I searched in this site: http://www.codeproject.com/Articles/5739/MATLAB-Shared-Library and I have tried the code, but also it didn´t work with the example in the page. Thank you for your time.