Many thanks. I had a look at the wix-router and I suspect I’ll be using it later when I have more of the site developed. For this particular functionality though I needed a client-side redirect to a 404 Not Found page. I have a repeater page - when the page opens, if the data satisfies a certain condition it needs to redirect to 404. I thought there might be a corvid ‘throw 404 exception’ command but in the end I was able to solve it using a wixLocation .to redirect.
wixLocation.to(baseUrl + “Not Found” );
The NotFound page does not exist on the site so this redirect will force a 404 response.