Restrict submissions by field

I am creating a register form for an event.

Users have to choose one room, so I need to restrict form submissions by room.

Something like this:
– Room A – 10 submissions
– Room B – 10 submissions

If Room A gets to 10 submissions, and the user tries to register for Room A, a message will “that room is full”. And the other way as well.

Is that possible to create? With calculations maybe?

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