double clicking row header

I would like to disable an event when I double click on the row header.

I have:
obj.setEvent("ondblclick", function(){this.action('dblclick')});
obj.setAction("dblclick", myfunction)

obj.getTemplate("left/item").setEvent("onmousedown", null);
obj.getTemplate("left/item").setEvent("dblclick", null);

but still when I double click on the row header, myfunction is executed.

Can anyone point me in the right direction. I am using version 1.

Thanks!