Load a XML dinamicaly through javascript

Hi,

I need your help.
I make a dinamic xml with a server side application and pass to it to parameters that can change depending in some clicked link.

I want when xml change then the grid content refresh and display the new data, but when I made this, and error is return.

I make:

var obj = Active..grid;

function xxxx(param1, param2) {
var data = new Active.XML.table;
data.setURL("xxxxxxxxxx");
data.setParameter("param1", param1);
data.setParameter("param2", param2);

data.request();

obj.setDataModel(data);
}

xxxx(value_param1, value_param2);

document.write(obj);

That is what I made in the page. When the page is loaded the grid is well generated, but when a new call to xxxx function with new parameters an error is shown (this._item[...] undefined). I debug all the proccess and the data object is well formed and obtain all the data, but the obj is not able to be refreshed.

Other questions:

How can I sort the grid for the first time if I don't know when I have recovered all the xml data? I overwrite the refresh method to make this and works, but I suposse this is not the best way to do that.

How can I put the tooltips in column 0, whith the data in the xml? If I follow the example code in your source, with a data array works, but with a xml file doesn't because the same problem as in the above question.

Thanks for your help and good job with the grid.