<script language="javascript">\n<!--\nfunction ClickHandler(src)\t{\n\tvar rb, lbl;\n\tvar tb = document.getElementById(\'<%=TextBox1.ClientID%>\');\n\tfor(i=0; i<src.rows.length; i++)\t{\n\t\trb = src.rows[i].children[0].children[0];\n\t\tif(rb.checked) {\n\t\t\tlbl = src.rows[i].children[0].children[1];\n\t\t\ttb.value = lbl.innerText;\n\t\t\t//alert(lbl.innerText);\n\t\t}\n\t}\n}\n//-->\n</script>

RadioButtonList1.Attributes.Add("onclick", "ClickHandler(this)");

<script language="javascript">
<!--
function ClickHandler(src)	{
	var rb, lbl;
	var tb = document.getElementById('<%=TextBox1.ClientID%>');
	for(i=0; i<src.rows.length; i++)	{
		rb = src.rows[i].cells[0].childNodes[0];
		if(rb.checked) {
			lbl = src.rows[i].cells[0].childNodes[1];
			if(document.all)	tb.value = lbl.innerText;
			else			tb.value = lbl.textContent;
		}
	}
}
//-->
</script>