Findcontrol in Web User Control

Have a page with a panel and a web user control. I want to use findcontrol in the web user control to find the panel in the first page Also uaing a master page but don't believe that has any bearing.
first page: <%@ Page Title="" Language="C#" MasterPageFile="~/Master/SiteEdit.master" AutoEventWireup="true" CodeFile="Page1Edit.aspx.cs" Inherits="Admin_EditPages_Page1Edit" %> <%@ Register Src="~/Admin/Controls/ImagesEdit.ascx" TagPrefix="uc1" TagName="ImagesEdit" %> <asp:Panel ID="pnlMain" runat="server" CssClass="pnlMain"> <uc1:ImagesEdit runat="server" ID="ImagesEdit" /> </asp:Panel>
user control code behind: (ImagesEdit,ascx) Panel pnl = (panel) FindControl("pnlMain");