How to have different headers for sections in a radRichTextBox

Hi again and thanks for your reply. It is exactly one month that I am trying to make this program but still not working. Look, I have the following code:

dd.Section section = new dd.Section();
dd.Paragraph paragraph = new dd.Paragraph();
dd.Span span = new dd.Span(this.txtHeader.Text);

paragraph.Inlines.Add(span);
section.Blocks.Add(paragraph);
dd.RadDocument document = new dd.RadDocument();
document.Sections.Add(section);

dd.Header header = new dd.Header();
header.Body = document;
this.radRichTextBox.ChangeSectionHeaderLinkToPrevious                           (this.radRichTextBox.Document.CaretPosition.GetCurrentSectionBox().AssociatedSection, dd.HeaderFooterType.First, false);
this.radRichTextBox.UpdateHeader                (this.radRichTextBox.Document.CaretPosition.GetCurrentSectionBox().AssociatedSection, dd.HeaderFooterType.First, header);

I want to make the program that whenever the user's cursor is in one section, he has the ability to change that section's header which the text of that is inside a textbox. I did your recommended way. I really do not know why it is not working.

Thanks a lot.