How can a custom-mounted drive show on desktop as mounted

[dg1727]

Hello, 

On Xubuntu 12.04.1, I have written a "udev" rule that calls a 
custom shell script to mount a USB ext4fs drive with custom mount 
options.  The drive gets mounted correctly so that the "mount" 
command shows the drive and the correct options.  On the XFCE 
desktop, however, the drive icon is grayed out, and the icon's 
right-click menu has an option for "Mount Volume."  

Is there a way to have XFCE update the icon automatically, as soon 
as the USB drive is inserted, to show that the volume is already 
mounted?  

I have tried:  

thunar-volman --device-added /sys$DEVPATH

where $DEVPATH is the sysfs path of the newly added device.  This 
command doesn't seem to do anything, including when I run the 
command in a terminal window (even with superuser privileges).  

Installed versions include xfdesktop 4.8.3, thunar-volman 0.6.1 

Thanks for any insight, including if I have missed something 
obvious.  

-dg1727