Dynamically Add OnClick Event To Select Element

I have a function that dynamically creates a new div, part of the function looks like:
root = document.getElementById('rootbox2');
var oDiv=root.appendChild(document.createElement("div"));
with(oDiv){
id=ji;
className="workshopRow";
setAttribute("attending","");
setAttribute("attending_count","0");
}
var oText = oDiv.appendChild (document.createTextNode(""));
var oDiv1=oDiv.appendChild(document.createElement("div"));
with(oDiv1){
className="workshopName";
}
var oText = oDiv1.appendChild (document.createTextNode(""));
var oSelect=oDiv1.appendChild(document.createElement("select"));
with(oSelect){
name="select_"+ji;
id="select_"+ji;
className="workshop";
onchange="calc_subtotal("+ji+")";
}
var oText = oSelect.appendChild (document.createTextNode(""));
var oOption=oSelect.appendChild(document.createElement("option"));
with(oOption){
value="12";
setAttribute("price",10);
}
What I am looking to do is add an onchange event to the select element, not sure if i have programmed it correctly but it does not seem to work.