Any other way to add nodes to a treeview from a table?

I have this code in my form's activate. But I get error every now and then.

OLE IDispatch exception code 0 from Nodes: Key is not unique in collection.

sele treeview
go top
=tableupdate(.t.)
do while .not. eof()
	if ckey="R"
		lonewnode = thisform.oletreeview.nodes.add(,,alltrim(ckey),alltrim(ctext)) <--- this is where the error comes up
	else
		lonewnode = thisform.oletreeview.nodes.add(alltrim(crelative),crelation,alltrim(ckey),alltrim(ctext))
	endif
	skip
enddo