Cannot reference Label with Dynamically Generated ID with ASP.NET VB - asp.net

Question

I have a page that queries a DB and displays information for a number of printers. I have several sections that I would like to update at different intervals client-side using AJAX (at least this is best solution my research has come up with). I can get AJAX itself to work with the common "Show the time" example without any issues.
My problem is that the IDs if the sections I want to update (I've tried span, asp:label, div...> are generated with the server side code and ends up something like "Label1", "Label2"...
Every time I try to update the text inside one of these generated labels I get "'Label1' is not declared. It may be inaccessible due to its protection level". Everything is within a form tag, everything is "runat="server"". I feel like I'm just missing a setting, or a reference to something. So far I haven't been able to narrow my searching enough to get a useful answer.
I've lurked around here for years and have always been able to find a solution. This has me stumped though.
---- Example -----
The end goal is to have better control of when and how specific elements are updated. This is using the Timer tutorial demo. In my application I would be assigning IDs for the labels based on a record ID from a query (i.e. ID = "Mach" & MID)
The original code that works as posted:
<form id="form1" runat="server">
<div>
<!-- Ajax button code start -->
<asp:ScriptManager ID="ScriptManager1" runat="server" />
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
<asp:Button ID="Button1" runat="server" Text="Ajax - Button" onclick="Button1_Click" />
</ContentTemplate>
</asp:UpdatePanel>
<!-- Ajax button code end -->
<br /><br />
<!-- Non - Ajax button code start -->
<asp:Label ID="Label2" runat="server" Text="Label"></asp:Label>
<asp:Button ID="Button2" runat="server" Text="Non - Ajax - Button" onclick="Button2_Click" />
<!-- Non - Ajax button code end -->
</div>
</form>
And the Code Behind
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs)
Label1.Text = DateTime.Now.ToString()
Label2.Text = DateTime.Now.ToString()
End Sub
Protected Sub Button2_Click(ByVal sender As Object, ByVal e As System.EventArgs)
Label1.Text = DateTime.Now.ToString()
Label2.Text = DateTime.Now.ToString()
End Sub
It seems to me the follow should work the same way:
<form id="form1" runat="server">
<div>
<% Call Generated()%>
</div>
</form>
Code Behind:
Public Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs)
Label1.Text = DateTime.Now.ToString()
Label2.Text = DateTime.Now.ToString()
End Sub
Public Sub Button2_Click(ByVal sender As Object, ByVal e As System.EventArgs)
Label1.Text = DateTime.Now.ToString()
Label2.Text = DateTime.Now.ToString()
End Sub
Public Sub Generated()
Dim str As String
str = "<div>"
str = str & ("<asp:ScriptManager ID=""ScriptManager1"" runat=""server"" />")
str = str & ("<asp:UpdatePanel ID=""UpdatePanel1"" runat=""server"">")
str = str & ("<ContentTemplate>")
str = str & ("<asp:Label ID=""Label1"" runat=""server"" Text=""Label""></asp:Label>")
str = str & ("<asp:Button ID=""Button1"" runat=""server"" Text=""Ajax - Button"" onclick=""Button1_Click"" />")
str = str & ("</ContentTemplate>")
str = str & ("</asp:UpdatePanel>")
str = str & ("<br /><br />")
str = str & ("<asp:Label ID=""Label2"" runat=""server"" Text=""Label""></asp:Label>")
str = str & ("<asp:Button ID=""Button2"" runat=""server"" Text=""Non - Ajax - Button"" onclick=""Button2_Click"" />")
str = str & ("</div>")
End Sub