JQuery auto upload with input=file form

I have this form

<form id="uploadFile" enctype="multipart/form-data">
    <h3>Upload a file:</h3>
    <input type="file" name="fileToUpload" id="fileToUpload" class="fileToUpload"/>
    <input type="submit" id="submit" value="Upload" name="submit"/>
</form>

And this jQuery code for the submit function (all in the same php file):

  $('#uploadFile').submit(function()
  {
    $old=$("#activity").html();

    event.preventDefault();
    $.ajax(
    { 
      url: "upload.php",
      type: 'POST',
      data: new FormData(this),
      contentType: false,
      cache: false,
      processData: false,
      success: function(data)
      {
        $('.info').html(data);   
        $('.info').show();

        $("#content").load("this_same_file.php"); 
      }
    });
  }); 

It works fine. What I need to do is to 'automate' the 'submit' call. I mean, once I clicked OK on the pop-up file window, I would like to submit automatically the form.

I tried to follow the suggestions posted on the thread How do I auto-submit an upload form when a file is selected? but the only thing I can do is a window.alert advertising me that I have clicked the OK button of the pop-up window.

How can I implement this feature in my code ? Thank you in advance for your help.