What is the best way to include content within an AJAX TabContainer?

Question

I didn't want to have a ton of code on one page, but to keep the code modular and simple. So in my TabContainer I have the following where each tab refers to a web page and my code is inside each web page. My TabContainer itself is inside the default.aspx page.

    <asp:TabContainer ID="tabTOL" runat="server" ActiveTabIndex="0" CssClass="tol">
        <asp:TabPanel ID="tabHome" runat="server" TabIndex="0" HeaderText="Home">
            <ContentTemplate>
                <iframe src="Home.aspx"></iframe>
            </ContentTemplate>
        </asp:TabPanel>
        ...

Of course, the problem is that I cannot refer to other tabs or the TabContainer/default page from within any tab. I'm trying to update a TextBox on the default.aspx page from a tab, but there is no reference to it.

Should I bite the bullet and have one huge web page with all the html and code behind? There are a dozen tabs in my TabContainer. I would think this would slow down processing as well. Or, is there a cleaner way to do this and still retain the ability to reference controls on the main page or other tabs?

I'm working in VS2008 and .Net 3.5 and AJAX 3.5.

Thanks!! Larry