Finding Value of Dynamic Control in MasterPage/ContentPage System

I have a page that creates dynamic textboxes based on the number of
fields a user chooses to fill out.

This process worked great when the page was standalone. However, when I
move to a Content/MasterPage setup, the MasterPage Form seems to be
interfering with the ability of my code to retrieve the value in the
dynamic control.

Are there any ideas on why this is happening or how to work-around the
problem? What is the syntax to find a dynamic control within a form
established on a Master Page? The two methods I have tried so far
always gets me the "Object reference not set to an instance of an
object" error.

A quick example is below. The name of the form established in the
MasterPage is "frmForm". I must place the form tags within the
MasterPage because of the presence of a SiteMap menu control that
resides in the MasterPage.

<%@ Page Language="VB" MasterPageFile="~/Sys_Masters/MasterPage.master"
title="Dynamic Control in Master Page" %>

<asp:Content ID="Content1" ContentPlaceHolderID="cphContent"
Runat="Server">

<script runat="server">

Sub Page_Load()

Dim txtbxTextBox As New TextBox()
txtbxTextBox.ID = "txtbxTextBox"
phPlaceHolder.Controls.Add(txtbxTextBox)

End Sub

Sub btnSubmit_OnClick(ByVal sender As Object, ByVal e As
System.EventArgs)

Dim txtbxTextBox As New TextBox()

'// Neither of the two methods below finds the control
'txtbxTextBox =
Master.FindControl("frmForm").FindControl("phPlace Holder").FindControl("txtbxTextBox")
'txtbxTextBox = CType(Master.FindControl("frmForm").FindControl
"phPlaceHolder").FindControl("txtbxExample"), TextBox)

lblValue.Text = txtbxTextBox.Text


End Sub


</script>

<asp:Label ID="lblTitle" runat="server" Text="Dynamic Control in Master
Page Test: "/>
<p />
<asp:PlaceHolder ID="phPlaceHolder" runat="server"/>
<p />
<asp:Button ID="btnSubmit" runat="server" OnClick="btnSubmit_OnClick"
Text="Submit" />
<p />
<asp:Label ID="lblValue" runat="server" />

</asp:Content>

Using a masterpage prepends a string onto the front of your control
names, usually something like "ctl00_<contentplaceholdername>_".
(replacing <contentplaceholdername> with the name of the
ContentPlaceHolder the control was created in.
You would then use FindControl("ctl00_whatever_yourcontrolname").
I have no idea why this is, it drove me nuts for a while.
Hope this helps.

Simon

Oops, I realized this morning that the page I was having that problem
in had never been run so I didn't realize that i was talking out of my
ass since that solution doesn't work.
What ended up working was first getting the ContentPlaceHolder control
and then using findcontrol from there:
ContentPlaceHolder mainContent;
mainContent = (ContentPlaceHolder)Master.FindControl("MainFormHo lder");

DropDownList ddl =
(DropDownList)mainContent.FindControl("controlname ");

That one ought to work for you, sorry about the idiocy :)
Simon