update progress bar with ajax and nodejs server with express framework?

i make a progress bar in a modalbox like this

<div class="progress progress-info">
  <div class="bar" style="width: 0%"></div>
</div>

i change the content of a div with ajax like this

function download_inicio()
{
    $.ajax(
    {
        url:'/inicio',
        cache: false,
        type: 'GET',
    }).done(function(web)
    {
        $('#contenido_nav_principal').fadeOut(600,function()//hide the div
        {
            $('#contenido_nav_principal').empty();// empty the div
            $('#contenido_nav_principal').html(web);//changing html 
            $('#contenido_nav_principal').fadeIn(600);// fade in the div
        });
    });
}

so i want to update the progress bar with the percentage of the receive data from the server... the data is the html received from the url:/inicio

the server is on nodejs listening on

app.get('/inicio',routes.inicio.inicio);

tnx all!