Here is somthing I have used, I had a comment next to it saying it only worked in VFP5, I really couldn't say for sure. Just something to paly with.

lctmp = 'some rich text data'
SET LIBRARY TO foxtools.fll ADDITIVE
IF openclip(0)
	lnformatnum = REGCLIPFMT("Rich Text Format")
	setclipdat(lnformatnum,lctmp)
	closeclip()
ENDIF
RELEASE LIBRARY foxtools