This is very old and may not work in later versions, but I remember many years ago using an undocumented method to create doclinks.
Defined In
NotesRichTextItem
Syntax
Call notesRichTextItem.AddLinkByIds( dbReplicaID$, serverHint$, viewUNID$, documentUNID$, comment$ [, HotSpotText$ ])
Parameters
serverHint$
String. ServerName in Canonical or Common format.
viewUNID$
String. UniversalID of the notesview you want to use for opening the document. Use an empty string ("") to create database link if no documentUNID is specified, or to use the default view for opening docLinks.
documentUNID$
String. UniversalID of the document you want to link to. Use an empty string ("") to create a view Link or database Link.
comment$
String. The text that appears when a user presses and holds the mouse pointer over the link.
HotSpotText$
Optional. String. If supplied, the HotSpotText will appear in the RichTextItem as boxed text which can be clicked on with the mouse to follow the link. In this case, no other token appears in the text.
Taken from:
http://searchdomino.techtarget.com/tip/Creating-DocLinks-using-undocumented-lotusscript-method