How to get textbox object

Hello!
I need to get value of dynamicly created textbox on
client script.
I use GetElementById("mytext") but it doesnt work.
Any help appreciated.
function addRowToTable()
{
var tbl = document.getElementById('tblSample');
var lastRow = tbl.rows.length;
// if there's no header row in the table, then
iteration = lastRow + 1
var iteration = lastRow;
var row = tbl.insertRow(lastRow);

// left cell
var cellLeft = row.insertCell(0);
var textNode = document.createTextNode(iteration);
cellLeft.appendChild(textNode);

// right cell
var cellRight = row.insertCell(1);
var el = document.createElement('input');
el.setAttribute('type', 'text');
el.setAttribute('name', 'txtRow' + iteration);
el.setAttribute('size', '40');
cellRight.appendChild(el);
}
function removeRowFromTable()
{
var tbl = document.getElementById('tblSample');
var lastRow = tbl.rows.length;
if (lastRow > 2) tbl.deleteRow(lastRow - 1);
}