Russell,
AstroArt can handle any autofocus requirements for ASCOM focusers.
(Manual p111-112)
I'm 100% sure that a simple script may do the job.
In fact John's AA5 Manager script package probably already does it.
He's very active on the AstroArt forum - check it out.
http://www.astroartforum.net/forum/forum.php
(I only use AA5 for spectroscopy - acquisition, guiding and processing)