Add row to XML Table Model

How can you add a row to the grid by adding a node to the xml dom object that is set as the data for the xml table model. My xml table model is populated by calling the setXML method and passing in an xml dom object that I retrieve via xmlHttpRequest. I want to allow my users to modifiy the data in the grid by opening a new window with a form that is auto-populated via the data from the row they selected. By changing the data in the form the data in the xml dom object is changed and hence when I call refresh() on my grid the data in the corresponding row changes. However when I try the same approach, but this time instead of modifying already existing data from the xml dom object I am adding a new node to the xml dom object which corresponds to a row in my grid, when I call the refresh() method the grid does not show the added row. I have been working on this for a couple of days and have sifted through this forum many times and cannot find a solution or even a reason why this sort of behaviour would be accuring. Any help would be greatly appreciated.

Thanks,