Google Analytics & this.selectedIndex : Information don't comes up
===

I'm trying to track a `onChange` action on a select list.
I need to return a selectedIndex, seams not working.

Here is my code:

    <select name="triOrdre" id="triOrdre" onchange="_gaq.push(['_trackEvent',Outils','Trier',this.selectedIndex]);">
    	<option value="myURL0">Option0</option>
    	<option value="myURL1">Option1</option>
    	<option value="myURL2">Option2</option>
    	<option value="myURL3">Option3</option>                  
    	<option value="myURL4">Option4</option>
    </select>

The information I need is 0, 1, 2, 3 or 4, regarding to the selectedIndex.
If I put `this.value`, I get the selectedValue (so myURL0, 2, ...).
But nothing is working with selectedIndex.

BUT:
If I try on Chrome with the GA debug pluggin, the pluggin see the trackevent with the expected values.
Ex: `['_trackEvent',Outils','Trier',1]`
but nothing appear in firebug or HTTPFox pluggin.


Thanks reading,
and thanks for you future help.

Jim.