Web Forms :: Controls Of Usercontrol Not Recognized In External Javascript?

I need to access controls of aspx page and usercontrol page through the external .js file. I created a global varaible in the aspx page

<script language="javascript" type="text/javascript">
var loadPanelID = "<%=ajaxLoadingPanel.ClientID%>";
</script>

Now I pass this value in the onclick event of button click (Let the funtion name be Fun(loadPanelID) ) . The controls is recognised in the .js file. Everything is fine till now. Now i need to call the same javascript method Fun() from the button click of usercontrol.

<script language="javascript" type="text/javascript">
var loadPanelID = "<%=ajaxLoadingPanel1.ClientID%>";
</script>

I have ajaxLoadingPanel1 in the usercontrol and I have defined global variable as in the first one in ascx and passed that value to Fun() method. But this time it gives error called "loadpanelID" is undefined.