So I just created a textbox with JavaScript like this:

EDIT: Added the len variable

var len = tbl.rows.length;
                     var rtb = tbl.insertRow(len);
                     var cName = rtb.insertCell(0);
                     var cDis = rtb.insertCell(1);
                     var cDur = rtb.insertCell(2);
                     cName.innerHTML = '<input type="text"  name="tbName1' + len + '" value="' + selected_text + '" >';
                     cDis.innerHTML = '<input type="text" name="tbDis1' + len + '" id="tbDis1' + len + '" >';
                     cDur.innerHTML = '<input type="text"  name="tbDur1' + len + '" >';
                     var txtBox = document.getElementById('tbDist1' + len);
                     txtBox.focus();

EDIT:Changed the second to last line. Still get this error: txtBox is null txtBox.focus();

The last line isn't working. After I create the textbox, I can't set focus to it. Is there any way of doing so?