I found this for Office 2016 - maybe this also works with office 2013 (version number has to be changed)
Through Registry Editor
You can also disable updates via the Registry Editor. Press “Windows key + R" to open the Run dialog, type regedit.exe. Your Registry editor window will open. Go to following Key
Then in the right-hand menu, an “Officeupdate" window will expand and shows you many keys. Double click on EnableAutomaticUpdates and set its value to “0". This will disable automatic updates of Office.
If you do not have any such value, create a DWORD value of 32bit by right clicking on the plane white area in the right-hand window of “Officeupdate" section. And name the DWORD value as “EnableAutomaticUpdates", set its value to “0".
Now close all windows, and Reboot your System once to apply all the changes.
It should work with hte hive 15.0 for Office 2013
I only found a german info from MS