Tiuz

Solved the problem now.

The solution if somebody else need something similar:

I installed Shortcode Exec PHP and created a new shortcode called ninja_setfield.

extract(shortcode_atts(array('id' => '0', 'val' => '0'), $atts));

global $ninja_value;
global $ninja_id;
$ninja_value= $val;
$ninja_id = $id;

function my_filter_function( $data, $field_id ){
  global $ninja_value;
  global $ninja_id;
  if( $field_id == $ninja_id){
    $data['default_value'] = $ninja_value;
  }
  return $data;
}
add_filter( 'ninja_forms_field', 'my_filter_function', 10, 2 );

And called the following shortcodes in my article:

[ninja_set_field id=17 val='2015-06-04']
[ninja_forms id=6]

Do you have any information about this. An example or a link to a guide would be really great 🙂