Help!!! Create Bootable USB Attack

Need help with creating a USB that I can drop outside of a building, so when someone there picks it up and puts it in their computer it will phone home to my IP on the net where I can be waiting for a reverse shell.

I tried using the Backtrack 5 SET (Social Engineering Toolkit) but I need something that will allow me not to be on the network and gain access to the network. Black Box Testing.

TX