Textbox selektieren in einem neu erstellten Tabpanel

<tabbox id="SampleSites" selectedIndex="0">
		<tabs onclosetab="alert('close')" closebutton="true"><!-- list of tabs -->
		       <tab>Sample: 1</tab> <!-- default tab -->
		</tabs>
		<tabpanels id="samplePanels"><!-- list of contents -->
			<tabpanel id="SampleDefaultPanel"><!-- default tab's content -->
			  <box orient="horizontal" flex="1">
				<groupbox id="GeoGroupBox">
					<caption id="GeoCaption" label="&GeoCaption.label;" />
					<grid>
					    <columns>
						<column id="GeoDescriptionColumn" />
						<column id="GeoTextboxColumn" />
					     </columns>
					     <rows>
						<row>
						   <description value="&TextboxColumnLabel.description;" />
							<hbox align="center">
							     <textbox id="LabelRow" value="" />
							     <image id="AddLabel" hidden="false" 
                                                               tooltiptext="&AddLabel.tooltiptext;" onclick="MegxSamCo.setLabel()"
							       style="cursor:hand" onmouseover="event.target.style.cursor='pointer'"
								onmouseout="event.target.style.cursor='default'" />
							</hbox>
						</row>
						<row>
							<description value="&TextboxColumnRegion.description;" />
								<hbox align="center"><!--onchange="sampleInfo.setLabel(this.value)" -->
									<textbox id="RegionRow" value="" />
									<image id="AddRegion" hidden="false"
									tooltiptext="&AddRegion.tooltiptext;" onclick="MegxSamCo.setRegion();"
									style="cursor:hand" onmouseover="event.target.style.cursor='pointer'"
									onmouseout="event.target.style.cursor='default'" />
								</hbox>
								</row>
								<row>
								     <description value="&TextboxColumnLat.Description;" />
							            <hbox align="center">
									<textbox id="LatRow" value="" />
									<image id="AddLat" hidden="false" tooltiptext="&AddLat.tooltiptext;"
									onclick="MegxSamCo.setLat()" style="cursor:hand"
									onmouseover="event.target.style.cursor='pointer'"
									onmouseout="event.target.style.cursor='default'" />
								</hbox>
							</row>
							<row>
								<description value="&TextboxColumnLong.Description;" />
								<hbox align="center">
									<textbox id="LongRow" value="" />
									<image id="AddLong" hidden="false" tooltiptext="&AddLong.tooltiptext;"
									onclick="MegxSamCo.setLong()" style="cursor:hand"
									onmouseover="event.target.style.cursor='pointer'"
									onmouseout="event.target.style.cursor='default'" />
								</hbox>
							</row>
							<row>
								<description value="&TextboxColumnDepth.Description;" />
								<hbox align="center">
									<textbox id="DepthRow" value="" />
									<image id="AddDepth" hidden="false"
									tooltiptext="&AddDepth.tooltiptext;" onclick="MegxSamCo.setDepth()"
								        style="cursor:hand" onmouseover="event.target.style.cursor='pointer'"
									onmouseout="event.target.style.cursor='default'" />
								</hbox>
							</row>
							<row>
								<description value="&TextboxColumnMaterial.Description;" />
									<hbox align="center">
										<textbox id="MaterialRow" value="" />
										     <image id="AddMaterial" hidden="false"
											tooltiptext="&AddMaterial.tooltiptext;"              onclick="MegxSamCo.setMat()"
											style="cursor:hand" onmouseover="event.target.style.cursor='pointer'"
											onmouseout="event.target.style.cursor='default'" />
									</hbox>
								</row>
							</rows>
						</grid>
					</groupbox>
				</box>
			</tabpanel>
		</tabpanels>
	</tabbox>

var MegxTabCo = new MegxTabController();


function MegxTabController() {


	sampleIdPrefix: 'SampleDefaulPanel';


	this.createTab = function() {
		var tabcount; // number of tabs
		var tabbox = document.getElementById("SampleSites");
		var tab = document.createElement("tab");


		tabcount = tabbox.tabs.childNodes.length;


		var serializer = new XMLSerializer();

		tabcount = tabcount + 1;
		tab.textContent = "Sample: " + tabcount;
		tabbox.tabs.appendChild(tab);


		var panelcontent = document.getElementById("SampleDefaultPanel");
		// todo catch missing panelcontent
		var prettyString = XML(serializer.serializeToString(panelcontent))
				.toXMLString();


		debugHere('pretty:' + prettyString);
		var clonePanel = panelcontent.cloneNode(true);
		clonePanel.id = '' + tabcount;
		var prettyString = XML(serializer.serializeToString(clonePanel))
				.toXMLString();


		debugHere(this.sampleIdPrefix + ', cloned: ' + prettyString);


		panelcontent.parentNode.appendChild(clonePanel);


	};


	this.removeTab = function() {

		var tabbox = document.getElementById("SampleSites");
		idx = tabbox.selectedIndex;
		debugHere("idx: " + idx);
		if (idx <= 0) {
			return;
		}
		tabbox.tabs.removeItemAt(idx);
		tabbox.tabpanels.removeChild(tabbox.tabpanels.selectedPanel);


		var panels = tabbox.tabpanels.getElementsByTagName("tabpanel");


		var myTabs = tabbox.tabs;


		for ( var i = 1; i < panels.length; i++) {
			var p = panels[i];
			var t = myTabs.getItemAtIndex(i);
			var j = i + 1;


			p.id = this.sampleIdPrefix + '_' + j;
			t.textContent = "Sample: " + j;
		}


		tabbox.selectedIndex = idx - 1;


	};
}

this.setSampleValue = function(elementId, value) {
		var tabindex = this.getTabIndex();
		debugHere("setSampleValue");

		if (tabindex == 0){
			setTextElementValue(elementId, value);
		}
		else{
			//try {

			var tabbox = document.getElementById("SampleSites");
				debugHere(tabbox);
				var nodes = tabbox.getElementsByAttribute("id", "MaterialRow");

				debugHere("nodes:" + nodes);


				for (var i = 0; i < nodes.length; ++i) {
					  var item = nodes[i]; 
					  var nodename = item.nodeName; 
					  debugHere("itemname: " + nodename);
					  var test = "test";
					  nodename.nodeValue = test.stringValue;
					  // Calling myNodeList.item(i) isn't necessary in JavaScript
					}			

		}

	};