I guess that event (onclick) was added dynamically...
It's quite an intricate job. To find which function is triggered onclick, you may do something like that: Make sure your button has an id, say id="myButton". It is not necessary, could be any other DOM way to refer that element, but for the following code (which is a basic example), you need that.
<script type="text/javascript">
document.onclick=checktarget
}
function checktarget(e){
var target = (e && e.target) || (event && event.srcElement);
if(target.id!='myButton'){return}
for(a in target){
if(a.match(/click/)){alert(target[a]);break}
}
}
</script>
The base idea of the code is to find which element (target in my code) on the document was clicked, and if it is that button, to circle trough all his properties to find the event attached called onclick (match(/click/) in my code), therefor to alert the value of that event - target[a] in my code -which value is exactly the function you are looking for. Of course, if you are looking for another event, you should modify the code accordingly.
But there is no way to find using a code where that function is. For that, I recommended you to use Firebug addon for FireFox as browser (use the Firebug's Search box)
