Hi Michael,
I don't have the time currently to figure this out and send you a working solution. So instead I'll share things I know:
1) if you inquire the window property "_QUBES_VMNAME" of the active window, you'll get the name of the qube
2) you should be able to get to this with wmctrl or maybe xdotool
Then write a little bash script in dom0 and hook it up to a shortcut, is what I think.
Good luck!
/Sven