How do I build an audience of people who already submitted our HubSpot form?

quick one. submissions from our HubSpot forms are coming into Croct now and I want to stop showing the lead magnet to people who already filled it in. instead I want to hit them with a next-step message.

so I need an audience that basically means "has submitted the form". how do I express that as a condition? the event is landing, I just do not know the right way to phrase "already converted on this form" so it evaluates per visitor.