Is this basically what you did using bookmarks? Obviously, the full code would check for the name of the bookmark but for this test I just referenced the one I knew was there, added the text I wanted after it, then deleted the bookmark.

oword=CREATEOBJECT("word.application")
odocument=oword.Documents.Open("c:\bookmarktest.doc")
obook= odocument.Bookmarks.Item(1)
orange=obook.Range()
orange.InsertAfter("the bookmark that I added")
odocument.Bookmarks.Item(1).Delete
odocument.Save()
odocument.Close()
oword.Quit