Because you have to open the file in Word, the answer is "yes, you can."
Just bear in mind that you can't save macros with .rtf format files in
recent versions of Word and you may have difficulty saving an attached data
source.

The easy way to do it is simply to insert the field codes in the usual way
in Word, then save the document as .rtf

If you do that, then open the .rtf as a text file, you will get some idea as
to how fields are encoded (e.g. typically there are tags for the field code
and separately for the last evaluated result). You should be able to find
the full current (Word 2003) v1.8 specification at
www.microsoft.com/downloads or by searching the http://msdn.microsoft.com 
site.

Peter Jamieson