Dcone on "[Plugin: WooCommerce - excelling eCommerce] Custom loop using multiple categories"

I'm trying to create a loop filtering by multiple categories.

I have the two product category slugs saved as variables.

Here are some loop args that work for me with just one category:

<?php
$args = array('post_type' => 'product', 'product_cat' => $catOne);
?>

But how do I filter by two categories? I have tried the following with no luck:
'product_cat' => array($catOne, $catTwo)

Any help would be greatly appreciated, thanks!

http://wordpress.org/extend/plugins/woocommerce/