Allow users to enter meta box field to create a field

Hi,

When creating a field, I have always included the details in an array like this:

array(
'label' => 'Text Input',
'desc' => 'A description for the field',
'id' => $prefix.'text',
'type' => 'text'
),

I want to allow the users of the plugin I’m creating, the ability to choose the type via a dropdown, & give the field a ‘label’ via a simple text field. How do I do this please? This will be done through a custom post type page.

Thanks!