There was recently some discussion about remembering xrandr parameters. As far as I can tell, this kludge adds an item to the .fvwmrc to toggle the auxilliary vga port on and off for at least one platform:
$ diff .fvwmrc.orig .fvwmrc
110a111
> + "Aux Video" Exec exec xrandr | grep -q "VGA
connected (" && xrandr --output VGA --auto || xrandr --output VGA --off
-Lars
