CRED – Add default value to a field without showing the field in the form

Hi,

I would like to add a default value to a custom field whenever someone submits a specific form. However I do not want that field to be visible on the form. I've found the documentation on cred_save_data and this looks like what I want. I'm just not sure how to edit this code for my use.

The field I want to give a value to is – "wpcf-email-newsletter"
The field is a checkbox which I would like to default as checked when the form is saved
The form id is "527"
The slug for the post type is – "organisation"

Here's the sample code given.

add_action(‘cred_save_data’, ’my_save_data_action’,10,2);
function my_save_data_action($post_id, $form_data)
{
// if a specific form
if ($form_data[‘id’]==12)

{

if (isset($_POST[‘my_custom_field’]))

{

// add it to saved post meta

add_post_meta($post_id, '__my_custom_field', $_POST['my_custom_field'], true);

}

}
}

Would someone be able to show me what needs changing to get it to work?

Thanks,

Charlie