Hi Mark Musacchio

Thanks for reaching out!

Unfortunately, we do not have such feature. There isn't currently a code you can enter upon opening an exam or quiz page/widget. You could suggest a feature though;
 We recommend posting this out on our Suggest a Feature page at this link: https://help.openlearning.com/category/ideas. Our Product team will take a look and consider implementing your ideas.

Let me provide you with a couple of workarounds which you may find useful. to try to achieve what you need at the time being.

1) You could restrict access to the page per class or have it open on a particular date as per Administer Students > Timeline. 

2)  You could set up an access code for the course itself via creating a separate class though. Please help the link to a help article below 
https://help.openlearning.com/t/y7al7s/how-do-i-set-up-a-private-access-code-

Hope this helps!