InnerHTML - Update Cells By Using A Drop List Selecting From Half A Dozen Items

I have a dynamic table where I would like to update cells by using a drop list selecting from half a dozen items. I have searched W3Schools for a tutorial but I am obviously looking in the wrong place. The working code I have thus far is:-

function insRow()
{
var x=document.getElementById('myTable').insertRow(1);
var a=x.insertCell(0);
var b=x.insertCell(1);
var c=x.insertCell(2);
var d=x.insertCell(3);
var e=x.insertCell(4);
var f=x.insertCell(5);
[Code]...