Office PowerPoint Add-in: update content after presentation started

I am developing an add-in for PowerPoint which receives data from a server with WebSockets. When data is received, I update the slide.

But, I want to know if it's possible to update slide content (Text, XmlSvg...) after the presentation is started? And how?

Currently, I update content like this but when I try during presentation, I got an internal error:

Office.context.document.setSelectedDataAsync(
 myText,
  {
    coercionType: Office.CoercionType.Text
  },
  result => {
    if (result.status === Office.AsyncResultStatus.Failed) {
      console.error(result.error.message);
    }
  }
);

Thanks for your help.