Non repeating random number

I am creating a spin wheel using Articulate Storyline. I am facing  a small challenge.

I have created 8 challenges with a wheel design using triggers. The wheel spins and stops on a random number, then it jumps to the allocated challenge. 
On the second spin, the same number might be repeated (Although, I added a trigger for each challenge) . For example: If the wheel stops on 2, the leaner faces challenge 2. This challenge must be marked as done and the wheel must NOT stop on 2 anymore. 

Is it possible to set up a "non repeating random number"?

Can anyone help me with it?

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