Preventing access to a room until a scene ends

Hello! I’m working in Inform 7, and I want the player character to be unable to access a room until an event is over. Is there anything I can write under the “when [scene] begins”/“when [scene] ends” to make this possible? If I can’t do this, is there a way that I can make it so an object can’t be picked up unless the scene is over? Thanks!

Instead of going to the Antechamber when the Explosion hasn’t happened, say “You can’t go in yet, the bomb is liable to go off any minute!”.

Thanks! I’ve reworded that to fit my story, but now I’m getting the ‘phrase not recognized’ error. My text is:
When Party begins:
Instead of going to the Meeting Room, say “The party is so crowded that there’s no way you’ll be able to get in there. Better wait for it to end.”.;

Is there anything else I should write?

“When [a scene] begins {…}” is a rule preamble. “Instead of {…}” is also a rule preamble. You can’t nest rules in that way; you have to use a single rule. “When Party begins {…}” is not going to help much: this is just a single event triggering, and can’t be used as a state in itself.

All you’ll need for this is an Instead rule, like so:

Instead of going to the Meeting Room when Party is happening, say "The party is so crowded that there's no way you'll be able to get in there. Better wait for it to end."

Aha! That worked perfectly. Thank you!