Mounting a squashfs filesystem in read-write

I have a Clonezilla installation on a USB stick and I'd like to make some modifications to the operating system. Specifically, I'd like to insert a runnable script into /usr/sbin to make it easy to run my own backup command to make backups less painful. The main filesystem lives under /live/filesystem.squashfs on the USB FAT-32 partition. How can I mount this read/write on my Linux machine in order to be able to add/remove/change files? I'm running an Ubuntu 12.04 derivative.