Thanks for the help.
Unfortunately you it is not quite that easy,
There are a few different ways to get the link that is used to capture where the update is being downloaded from, you can monitor the log files and see if something prints out that identifies what the URL might be. I think that this method would be less reliable and would require you to download the android adb drivers.
The other method, would be to monitor the network traffic of the NSZ-GS7 using an application such as Wireshark http://www.wireshark.org/.
The idea here would be for you to route all your network traffic through a computer with Wireshark installed, into your NSZ-GS7. This can be done either by plugging a computer into your router via LAN, and turning your computers wireless router and connecting the NSZ-GS7 to the hotspot created by the computer. Anther user has posted instructions on how to do this here, http://forum.xda-developers.com/showpost.php?p=25450500&postcount=25.
I think it is easier to connect your computer via wireless connection, read WiFi, and then sharing your connection to the NSZ-GS7 via LAN, this can be done simply within the settings of your wireless adapter, on Windows 7 at least. Then you would follow the same instructions in the post above.
the link that you would be looking for would be in the form,
http:/ /android .clients. google .com/packages/ data/ota/sony_beetle /XXXXXXXX.REL03_NSZGS7_CA2_1104_4384_20120724_URSC_S6725.zip
with the X's replaced with some string of letters and numbers.
The file will be downloaded in the background and you need to be monitoring the traffics before the download happens, it wont work after. So you would need to watch the traffic from the time that the device is first connected to the network, until the download initiates.