[power-pro] How to use a variable "volume"

[don_ac64]

I wish to make a script like this:

For (volume==variable)
*Format Item item 1 list "Tray" iconfile "C:\WINDOWS\system32
\shell32.dll" iconnum variable
Endfor

so that I can automatically change a tray icon depending on the value 
of the variable volumeAll.
But I couldn't make it working.
I don't know how to use the variable "volume" so that it's value could 
be used as the last argument of the Format item command.