be sure to set the ID of the cell you want to work on

function CyJS_Utils_insertRow()
{
myTR=myTable.insertRow();
alert("myTable has now "+myTable.rows.length+" rows");
// you have to add also cells into the newly created row!
myTD=myTR.insertCell();
myTD.innerText="Hello";
myTD=myTR.insertCell();
myTD.innerText="new cell";
}

Table name : mySumTable