I have prepared a quick Add-In that produces these in Word 2013 using that field. The code you are looking for is called a QR bar code.

You can download the Add-In at Add-Ins. It prompts for the text you want the code to reflect and will produce the code.



The code below was produced by the Add-In and gives the download page:


Hope this helps. To use it, put it in your Word Startup Folder. Next time you start Word 2013 a new icon will appear on your QAT. That icon (a striped box) will run the macro.