dynamically populate select list

Hi,

I am trying to use the following filter to dynamically populate a select list (af/field/prefill_value) but it is not working. This is the code i have:-

[CODE]
function prefill_form_field( $value, $field, $form, $args ) {
$field[‘choices’] = array(‘key_1’ => ‘value 1’, ‘key_2’ => ‘value 2’);
return $field;
}
add_filter( ‘af/field/prefill_value/key=field_5fc7aec97ca22’, ‘prefill_form_field’, 10, 4 );
{/CODE]

Thanks