Taxonomy Field: Allow users to create mutiple new terms when submitting the post

Hi,

When I add a taxonomy field to a meta_box:

array(
    'name' => 'Taxonomy',
    'id' => 'taxonomy',
    'type' => 'taxonomy',
    'taxonomy' => 'category',
    'field_type' => 'select_advanced',
    'add_new' => true,

)

I can only add one new term to the post when submitting the form.
Would it be possible to let users add multiple new terms to a post?

Thanks in advance.

Cheers,

Tako