Turniej par

lthough you should have to add some validation, this action does not seem to be complicated for the current version of WordPress.

Basically you need two steps to add a Custom Field to a Custom Post Type:

1. Create a metabox which holds your Custom Field
2. Save your Custom Field to the database

These steps are globally described here: http://wordpress.org/support/topic/is-it-possible-to-add-an-extra-field-to-a-custom-post-type