Constant:

LL_RTF

Content e.g.:  

"{\rtf1\ansi[...]Hello {\b World}!\par}"

Hint:   

The variable content must start with "{\rtf" and contain RTF-formatted text.

Important: The rendering of RTF contents in variables and fields is optimized for contents created with Microsoft's RTF control. These can be generated e.g. by using the Windows Wordpad application. Contents generated by Microsoft Word may not conform to the Windows RTF control's RTF standard and should not be used.