Get Pane.ID from Dynamically Created Accordion Panel When Accordion SelectedIndexChanged

I've been at this for days without success. I have an accordion panel that is being created dynamically. One of the items in the accordion panel is the pane. The paneis given the ID of the record in the database that is populating that pane in the accordion. As an example, if I was creating an accordion for each of the 50 states, the paneID would represent the states admission order (i.e. Delaware, Pane.ID = "Pane_1", New Jersey, Pane.ID = "Pane_3", Hawaii, Pane.ID = "Pane_50", etc.)

I need to be able to pull the ID of the pane when the user selects the Accordion. I've added the following script to the page that binds top the selectedIndexChange event of the accordion:

function pageLoad() {$find('<%= Accordion1.ClientID %>_AccordionExtender').add_selectedIndexChanged(
        accordion_selectedIndexChanged);
        };

function accordion_selectedIndexChanged(sender, args) {
            var sinx = sender.get_SelectedIndex();
            alert(sinx);
        }

This works in that it fires when I select the Accordion pane. I don't know how to get the Pane.ID from this point on in the accordion_selectedIndexChanged function.