Start rectangle selection on event

Hi,

I'd like to start a rectagle selection on events. If I press 'shift + click' it starts the rectangle selection with no problem, but I'd like the same behaviour without 'shift' key.

I've tried this:

dp.onGridMouseDown = function(args) {
args.action = "RectangleSelect";
};

But it only works when the selection starts outside an event.

Is there a way to start a selection on events without pressing 'shift' key?