Why don't you use rad Ajax and AjaxPanel - this way, you can easily change the visibility of any control - just make sure it is embedded inside ASP:Panel, as described in this online help topic:http://www.telerik.com/help/aspnet/ajax/ajxMostCommonMistakes.html
Showing/Hiding controls with ajax
The visibility of controls is best controlled during the ajax request if they are placed inside a control on the page that is always visible. Here are the exact steps:
1. Place the control in an element which is always visible, such as a Panel, an AJAX Panel or a DIV.
2. Add this visible control to the AJAX pairs where the AJAX initiator control should update the visible control.
3. Change the Visible property of the control you want to hide/show.