How to remove an option to the menu on the Form

Hi guys,

I'm creating a escape room form, so the group can select the room and time they want to play.
There are 3 rooms (each one with 5 different times to play).

When a group select the room/time (example: Room 1 - 20h) this room can't appear on the form anymore.
How can I do that?

I read in other message here to create a new table with all the possibilities (I already did that), and created a link to another record in the main table (which is used to create the form).
I tested it but it didn't work.

If anyone could help me, I appreciate it! Thanks