Hello Kevin,

this is my meta-box code. I want to validate the three fields fvb_shipping_date, fvb_event_date and fvb_return_date.

/*
Title: Termine
Description: Bestellte Produkte
Post Type: fvb_order
Capability: manage_options
Context: side
Priority: low
Order: 1
Locked: false
Collapse: false
Meta box: true
*/

piklist('field', array(
    'type' => 'datepicker'
    ,'field' => 'fvb_event_date'
    ,'label' => __('Veranstaltungsdatum', 'fvb_de')
    ,'options' => array(
        'dateFormat' => 'yy-mm-dd'
        ,'firstDay' => '1'
        ,'minDate' => '0'
    )
    ,'required' => true
    ,'on_post_status' => array(
        'value' => 'reserved--closed'
    )
));
piklist('field', array(
    'type' => 'number'
    ,'field' => 'fvb_event_period'
    ,'label' => __('Dauer', 'fvb_de')
    ,'description' => 'Tag(e)'
    ,'value' => 1
    ,'on_post_status' => array(
        'value' => 'reserved--closed'
    )
    ,'validate' => array(
        array(
            'type' => 'limit'
            ,'options' => array(
                'min' => 1
            )
            ,'message' => 'Min 1 day.'
        )
    )
));

piklist('field', array(
    'type' => 'datepicker'
    ,'field' => 'fvb_shipping_date'
    ,'label' => __('Versand', 'fvb_de')
    ,'options' => array(
        'dateFormat' => 'yy-mm-dd'
        ,'firstDay' => '1'
        ,'minDate' => '0'
    )
    ,'required' => true
    ,'on_post_status' => array(
        'value' => 'reserved--closed'
    )
));
piklist('field', array(
    'type' => 'datepicker'
    ,'field' => 'fvb_return_date'
    ,'label' => __('Retour', 'fvb_de')
    ,'options' => array(
        'dateFormat' => 'yy-mm-dd'
        ,'firstDay' => '1'
        ,'minDate' => '0'
    )
    ,'required' => true
    ,'on_post_status' => array(
        'value' => 'reserved--closed'
    )
));