Dynamic Option Selected Value From Form

Here is my options select from my form. Its dynamically generated with php.
Code:
<select id="upgrade[]" name="upgrade[0]" onchange="javascript:calTotal(this);">
<option value="1">1</option><option value="2">2</option>
</select><br />
<select id="upgrade[]" name="upgrade[1]" onchange="javascript:calTotal(this);">
<option value="1">1</option><option value="2">2</option>
</select><br />
<select id="upgrade[]" name="upgrade[2]" onchange="javascript:calTotal(this);">
<option value="1">1</option><option value="2">2</option>
</select><br />

Using javascript I want to get the selected value. Here is what I have, but its getting no where:
Code:
function calTotal(aVar)
{
var c = document.getElementsByName(aVar);
c = c.length ? c : [c];
for(var i=0; i<c.length; ++i)
{
if(c[i].value==1)//I am getting undefined here
{
}
}
Is there a way to loop through an array of option selected like the one I have here?