I think Ipac works by emulating a keyboard so in theory you should be able to open a program like notepad and type out letters and numbers using the switch terminals on the ipac.

If you are feeling flush I would recomend a pokeys board. It does a very similer thing but it is custom built for mach3 and comes with its own plugin. You can also use MPG's and pass back encoder info to mach for a realtime DRO.