I looked it up in the addendum for ethernet and hard drive; it looks like you can do M98 from the hard drive.
Go to this link, scroll down until you get to manual addendums and then you will see Ethernet/Hard drive Option. Click on that and you will find what you need on pages 4 and 5 under the section about File Numeric Control (FCN) Operation.
http://www.haascnc.com/custserv_updates.asp#manualupd