Change contents of an external update panel from within a seperate accordian panel?

I am trying to update the contents of an update panel from the event of changing the panel in the accordian control (located outside of the update panel I wish to update). When I try to creat a trigger the update panel does not see the button located inside the accordian control. Any suggestions?

Let me see if I can clarify my question further. I have a content container on a master page. Inside the content container I have a table with two cells. In the first cell I have am using the accordian control. when I click on one of the headers in the accordian control I want it to update an update panel in cell number 2. The content of the accordian panel will be just a brief headline and overview of what is displayed in the update panel in cell #2. My issue is that when trying to define triggers in the update panel in cell #2 it does not see any of the controls in cell #1. Any suggestions?

Thanks for any help you can provide.