Custom User Controls Randomly Displayed like Adrotator

 I have several user controls I made that display different data, like a testimonial, or new client, or most referrals, or prize drawing winners. I also have one page using querystring that displays 10 different page info. So I do not want the same control to display on each page, but a random one. Now I know you have to register each control on the page; but would like to program it on C# to display a random control.
<%@ Register src="../App_Controls/Testimonials.ascx" tagname="Testimonials" tagprefix="uc1" %> <asp:Content ID="contentHead" ContentPlaceHolderID="head" runat="server"> </asp:Content> <asp:Content ID="contentSide" ContentPlaceHolderID="side" runat="server"> <uc1:Testimonials ID="Testimonials1" runat="server" /> </asp:Content>
How do I programtically access ...