Update updatepanel from within a ajax modalpopup

I have a aspx page with a ajax modalpopup control in it. I need to update the contents inside an updatepanel on the page(not inside modalpopup) when I do a button click inside the modalpopup.

So I can display the changes inside the updatepanel without a full page refresh. I already tried using the UpdatePanel.Update() method inside the code behind of the button click event. But it does nothing.

What I'm doing right now is make a full page refresh inside the button click event.

there anyway that I can update the update panel to display the changes?