function custom_process_order($user_id) {

    global $woocommerce;
        $order = wc_get_order($order_id);

    $amount = intval($order->get_total());
    $funds = get_user_meta( $user_id, 'account_funds', true );
    $funds = $funds ? $funds : 0;
    $funds += floatval( $amount );
    update_user_meta( $user_id, 'account_funds', $funds );

}