add_action( 'frmapi_post_response', 'frm_get_api_response', 10, 3 );
function frm_get_api_response( $response, $entry, $form_action ) {
	$status = wp_remote_retrieve_response_code( $response );
	if ( $status == 200 ) {
		add_filter('frm_main_feedback', 'frm_add_200_to_message' );
	} else {
		add_filter('frm_main_feedback', 'frm_add_500_to_message' );
	}
}

function frm_add_200_to_message( $message ) {
	$message .= ' The API call was successful';
	return $message;
}

function frm_add_500_to_message( $message ) {
	$message .= ' The API call was not successful';
	return $message;
}

add_action( 'frmapi_post_response', 'frm_save_api_response', 10, 3 ); 
function frm_save_api_response( $response, $entry, $form_action ) { 
	$body = json_decode($response["body"], true); 
	$returned_id = $body["CHANGEME"]; // this line will change based on the API you are sending to 
	if ( $returned_id ) { 
		FrmProEntryMeta::update_single_field( array( 'entry_id' => $entry->id, 'field_id' => 12, // change to the ID of the field to change 'value' => $returned_id, ) );
	} 
}