How to append a text line in stringbuilder and save to MS Office RTF file.

Question

Hi there, I have been trying for a many hours how I can append  a line to a rtf file.
My program reads from a template and then replaces some values in the template with values from a dataset then save it into another Microsoft Office rtf file.  The trouble is, I can replace the values however I cannot put a line break in there.
I have tried System.Environment.NewLine, vbCrlf, "L\n" (ithink this is what i used) and also stringbuilder.AppendLine(string) and stringbuilder.AppendLine
The above works if I was to save the string into a ".txt" extension but it will not work if I save string into ".rtf" or ".doc" extension.
I am hoping someone can help me out.
Thanks