Autosubmit Flexiform

First a little about what I am trying to achieve. The goal is, to have a very simple field on a page, where a user can either drag&drop images, or click to browse images.
Once these images are dropped into the field, they should upload automatically. No submit button at all.

This is what I have done so far.
1. I created a content type, with a image field.
2. Drag&Drop is done using the “dragdropfile” module.
3. The form is exposed in a Panel page using the “flexiform” module and the “panels” module.
4. All unnessasary stuff is hidden using CSS.

This is how far I got so far:…

The only thing left, is to get rid of the submit button. I found this article, describing how it can be done. But this is the part where I have some difficulties.

The form on the page has id: “flexiform-image-upload-form” – but I fail to catch the form in template.php. I tried using the following ID’s:

And the code:

function MYTHEME_form_alter(&$form, &$form_state, $form_id) { 
if ($form_id == 'FORM_ID') {
	echo "You got me!";

So my question is, how can I autosubmit my form, after a user has dropped some images into it?

Drupal version: