Override pods field in form

Hi,
I’ve created a shortcode to display a pods form for submitting in the front end.
My custom post type has a drop-down field with 2 values, and these values are displayed depending on some conditions.

So, for example, when a condition is met both values should be in dropdown. For another condition, only one value.
I can make the conditions, but I don’t know how to override the field.

This is my code:

$mypod = pods( 'ad_post' );
	// Override the options of a specific field
	$fields = array( 
		'post_title' => array('label'=>'????? ???????'), 
		'website' => array('label'=> '??????'),
		'ad_position_field' => array('label'=> '???? ???? ???????'),
		'ad_image' => array('label' => '???? ???????')
	);
	// Output a form with specific fields
	return $mypod->form( $fields, '?????' );

The ‘ad_position_field’ should have this condition.