VMware will allow you to route the hosts serial port through to the guest OS.
Anyway, I remember DOX5. Despite that it has won a price in 1985, I really really cannot recommend using it today, not even for a home or training project. Sorry to say MrQ, but DOX5 is one of the worst programming environments I have ever tried.
PLC_User, if this is a real running installation, then you should think about migrating to a newer PLC.
Hopefully you have a printed program listing with comments somewhere. If you do have a printed program listing, then you dont have to mess around with DOX5.