reset text fields populated with XML to blank

I have data loading into one of X number of colums when a button is pressed. So button 1 is pressed and text for button one loads into say 4 columns. Then when button 2 is pressed, it may load into 2 columns.

What is happening in this example is the data for button 1's remaining two columns is still showing. Button 2 only has XMl for the 2 columns.

I tried resetting the value of the text as indicated below but it does not remove the colums which are not needed.

_root["but"+b].onRelease = function() {
var path = "buttongroup/but[@id='"+this._name+"']/column";
var myCols:Array = XPathAPI.selectNodeList(myXML.firstChild, path);
for (var j = 0; j<myCols.length; j++) {
_root["c"+j+"_txt"].htmlText = ""
_root["c"+j+"_txt"].htmlText = myCols.firstChild.nodeValue;
}
};