Certainly you can invoke an agent from Access — but you can’t pass parameters to an agent, even from within Notes/Domino, other than the NoteID of a saved NotesDocument. That being said, there’s no need to fire an agent — you have to connect to Notes via COM to invoke the agent anyway, and would need to create a document with which to pass params, so why not create the message directly in your Access code? The COM methods are nearly identical to Lotusscript, the only real difference being how you get a new NotesSession. (If the version of Access you are working with allows early binding and library references, you want to create a reference to Lotus Domino Objects.)
Dim s As NotesSession
Set s = CreateObject(“Lotus.NotesSession”)
You will also need to grab a database from which to send the mail — any database will do in a pinch. See Lotus Domino Designer Help under LotusScript/COM/OLE Classes -> LotusScript Class coding guidelines -> Accessing the Domino objects through COM for more details.