Hi,
It appears that you need to put in some JavaScript code. :) There are two ways to trigger the CallbackPanel. One with trigger and the other with JavaScript code.
Using trigger is easy. You simply edit the CallbackPanel's trigger collection. There is one feature that may help you, is that you can actually use the parent control as a trigger. For example, if you have a Panel that includes two ImageButtons, you can set the Panel as a trigger instead of setting those two ImageButtons as triggers. Set a parent control as a trigger would enable all child controls as triggers.
The other option is to use eo_Callback client side JavaScript function:
http://doc.essentialobjects.com/library/1/jsdoc.public.global.eo_callback.aspxThis is a JavaScript function that you can call anywhere in your client side code (Obviously you will need to figure out how and where to call this function). The function triggers a callback and brings you back to the server side, where you can do whatever you want such as updating another control inside the CallbackPanel. The key difference between this approach and the trigger approach is this approach is not directly associated with a "trigger control", so you do not have a distinctive event handler on the server side to fill. On the other hand, if you use the trigger approach, for example, a standard Button as a trigger, you would do whatever you want to do inside your server side Button_Click handler. When you use JavaScript to trigger Callback, such Button_Click handler doesn't exist because the callback wasn't directly triggered by any control at the very first place. As a result, you can perform your action mostly in two places: Page_Load and Callback_Execute handler. If you do it inside Page_Load handler, you usually will need to have code to check whether the current request is a callback:
http://doc.essentialobjects.com/library/1/eo.web.callbackpanel.iscallback.aspxhttp://doc.essentialobjects.com/library/1/eo.web.callbackpanel.iscallbackbyme.aspxYou can also handle the CallbackPanel's Execute event, however that event is fired at a relative late stage of the page's life cycle, so it may or may not work for you.
Hope this helps. Please feel free to let us know if you have any more questions.
Thanks!