Computed Fields isn't doing .... anything!

I am trying to combine 3 fields into one section for use during the node creation process.

In other words, when someone creates an "article" node, I'd like them to be able to submit an MP3, a PDF, and a little Test, all right next to each other like so (see attached or click here).

So I am using the code given here

And in the computed code field, I put:

// set temp variable
$count = 0;

// put array into computed field array pt1
foreach (element_children($node->field_audio) as $key) {
    $node_field[$count]['value'] = $node->field_audio[$key]['value'];
    $count++;
}

// put array into computed field array pt2
foreach (element_children($node->field_pdf) as $key) {
    $node_field[$count]['value'] = $node->field_pdf[$key]['value'];
    $count++;
}

foreach (element_children($node->field_desc) as $key) {
    $node_field[$count]['value'] = $node->field_desc[$key]['value'];
    $count++;
}

Where the:

• field_pdf takes in a pdf file upload
• the field_audio takes in an MP3 audio upload (and on the node view, it uses SWTTools module to make it playable on the site)
• and lastly field_desc is just textfield.

I display this field with just:

$display = $node_field_item['value'];

I have it set to "unlimited" Number of values, so indefinite numbers can be added.

Under the "Display Fields" tab, this is what I have going:
Image Link

Is what I am looking to do possible? If so, how come this computed field isn't working? (Its actually not doing anything at all!)