How to display the list of available options in a sharepoint form

I have a simple added sharepoint form called & # 39; laptop loan application & # 39; It has the employee's name, date and laptop as fields. The laptop is a column of choice: surface, thinkad and laptop. There are only three devices physically present in the client.

Now the following seems difficult to implement:
1. Suppose a couple of users have requested and acquired thinkpad and laptop, so only the surface is available to request.

If the following person submits a thinkpad request, how do I prove that it is not available or I cannot restrict the thinkpad request?

Please share your thoughts if there are any, thanks I am working SP online modern.