Updating Layer Markers

I need to update Layer Markers from the source using extended script. I was earlier using the following

var activeItem = app.project.activeItem;

var bodyComp = app.project.items[6];

bodyComp.openInViewer();

var selectedLayer = bodyComp.layers[7];

selectedLayer.selected = true;

app.executeCommand(2539);

For this to work the GUI needs to remain open. Im using aerender.exe to render and want to execute the jsx using it. I don’t want the GUI to remain open. Is there any other way of updating the layer marker from the source. E.g. Audio Layer marker from audio source file.