How do I add a node to a nodelist

I am trying to use two two widget control and want to let the user move rows between the controls. I am using XML data. When I have rows in both the controls, moving seems to work fine. But when one of the control is empty, it throws an error. How do I do this?

I am using objNodeList.item(0).parentNode.appendChild(objNewNode). When I don't have any items, how to I get the parent Node (which is not equal to objNodeList).

Thanks,