The following config disables selecting a time range using right mouse button:
dp.timeRangeRightClickHandling = "Disabled";
dp.onGridMouseDown = function(args) {
var button = DayPilot.Util.mouseButton(args.originalEvent);
if (button.right) {
args.action = "None";
}
};
Note that you will need build 8.2.2222 from the sandbox:
http://javascript.daypilot.org/sandbox/
Earlier builds don't support args.originalEvent property.