/// <param name="Start">Where the chunk's own content starts: its page, its sheet and row, or its line.</param>
/// <param name="End">Where the chunk ends. Equal to the start when the chunk stays within one page, row or line.</param>
/// <param name="AttachmentPosition">Which attachment of a mail the chunk is from, counted from zero as the index numbers them, or null for the text of the mail itself and for anything but a mail.</param>