Hi, I think this should have been posted in the Axon forum actually. The way it works is, the SIPURA adapter never actually deals with IVM, everything is done through Axon. The SIPURA connects to Axon, Axon connects to IVM.
Anyway, please check out my "Ultimate guide" to getting your SIPURA adapter to work with Axon (and other NCH phone applications like IVM) here:
http://nch.invisionzone.com/index.php?showtopic=5091