Remove parts from AppleScript result
Try something like this:

set mydisks to list disks
set newdisks to {} as list
repeat with currentdisk in mydisks
    if ((currentdisk as string) is not equal to "net") and ((currentdisk as string) is not equal to "home") and ((currentdisk as string) is not equal to "Macintosh HD") and ((currentdisk as string) is not equal to "MobileBackups") then
        set newdisks to newdisks &amp; currentdisk
    end if
end repeat


You will have your desired list on newdisks.