How can I add a timeout phase for retries to a quiz?

I would like to make a function where if a user fails a quiz 5 times, they cannot retry the quiz until 5 minutes has passed. 

I currently have a variable named retries and when its value reaches 5, a layer named timeout  which will show to cover the quiz's start slide so the user will not be able to access it. Every time the user clicks the 'start' button on the start slide, +1 is added to the retries variable.

When 5 mins expires, I want to hide the timeout layer and reset the retries variable back to 0.

Does anyone have any advice on how to include a timer which will count down from 5 mins independent of which slide the user is on? I had the idea of just making a 'retry' button appear when the timeline is at 5mins, but the user will have to stay on that slide. It would also be cool for the user to see where the timer is at (ex. 4:30....3:21...2:10...0:90...retry available!).

thank you!