Read this carefully:
http://notes2dekiwikisample.wik.is/Lotus_Cpp_API/01_Reference_Guide/LNNote_Class/LNNote::CreateItemYou should use CreateItem only once, then you use the proper method to append rich text.
A good manual, still valid probably:
http://www.redbooks.ibm.com/redbooks/pdfs/sg244876.pdfSee page 554 (562 in the PDF Reader)