def calc_change_percent(current_value: int or None, previous_value: int or None) -> int or None:
    """Calculate change percent.

    Args:
        current_value: The current value.
        previous_value: The previous value.

    Returns:
        Percent.

    """
    return (
        round((current_value - previous_value) / previous_value * 100)
        if current_value is not None and previous_value
        else None
    )