How can I cast my desktop to a Chromecast dongle without having the sound coming from my laptop?

Within the Chrome browser (on Windows) there is the option either to cast the current tab or the whole screen (desktop) to the dongle.

When I cast a tab, then the PC's sound is turned off (unless it is already muted), but the sound is transferred to the dongle along with the picture for normal viewing on the TV screen.

However, the Chrome browser does not handle all video types. If I cast the desktop, I can open a player such as VLC over the top of Chrome so that the whole screen is showing the VLC window and play videos in other formats. This gets mirrored through the dongle and TV. However, the PC's sound remains active, and as the mirrored image on the TV is one or two seconds behind what is on the PC, I get two separate audio sources that are one or two seconds apart. If I mute the PC, then the sound from the TV is also muted.

Is there any simple setting that will allow me to turn off the sound from the PC but still keep it on the TV when I cast the desktop?