ModalPopupExtender in an ASCX cannot return value

I have an ASCX  form  call it ASCX-1 that opens another ascx ModalPopupExtender that displays a listview call it ASCX-2. ASCX-1 sends a paramter to ASCX-2 which opens fine. However, upon making a selection I want to fill in a textbox on ASCX-1 based on the selection made on ASCX-2.

ASCX-1:

<table border="0"><tr><td  align="right" width="90px"><asp:Label ID="Label_comments" runat="server" Text="Comments" CssClass="Form_Label_Font"></asp:Label></td><td  align="left" width="340px"><asp:TextBox ID="txt_comments" runat="server" Text='<%# Bind("comments") %>' CssClass="Form_Input_Font" MaxLength="200" Width="340" Rows="4" TextMode="MultiLine" ></asp:TextBox></td><td  align="left" width="20px"><asp:PlaceHolder ID="Comments_PlaceHolder" runat="server"    /></td></tr></table>

In the code behind I call ASX-2 via the Comments_PlaceHolder

This is the ASCX-2

<%@ Control Language="vb" AutoEventWireup="false" CodeBehind="comments_popup.ascx.vb" Inherits="wo.comments_popup" %><%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="asp" %><asp:UpdatePanel ID="UpdatePanel_Comments_PopUp" UpdateMode="Conditional" runat="server"  EnableViewState="false"  ><ContentTemplate><table style="border-width: 0"><tr><td style="width: 18px; text-align:left; vertical-align: top; background-color:#349cf1;"><asp:Button ID="Comments_PopUpButton" runat="server" BorderWidth="0" Width="18px"
                                        Text="..."
                                         Height="25px"  BackColor ="#349cf1"
                                         Font-Names="Tahoma,Arial, Verdana"
                                         ForeColor="White" Font-Size="11px" /></td></tr></table><asp:ModalPopupExtender ID="ModalPopupExtender_Comments" runat="server" BackgroundCssClass="modalBackground"
    DropShadow="true" TargetControlID="Comments_PopUpButton" PopupControlID="Comments_Panel" 
    CacheDynamicResults="false" CancelControlID="ImageButton_Back" ></asp:ModalPopupExtender><asp:Panel ID="Comments_Panel" runat="server" BackColor="#c6e0f9"  Style="display: none"
    CssClass="modalPopup" ><table style="width: 600px" ><tr><td style="width: 46px; background-color: #4A4344; text-align: center; vertical-align: top"><asp:ImageButton ID="ImageButton_Back" runat="server" ImageUrl="../images/nav/white/back.png"
                    Width="36px" Height="36px"  /></td><td style="width: 10px; background-color:inherit; text-align: center; vertical-align: top">&nbsp;</td><td><asp:Label ID="lbl_Select" runat="server" Text="Comments:" CssClass="Form_SubTitle_Font" /><div id="Div_ListView_Comments" style="height: 270px; overflow: auto; border: 2 solid black;"><asp:ListView ID="ListView_Comments" runat="server" DataKeyNames="wo_comments_uniqueid" 
                                    DataSourceID="SqlDataSource_comments_PopUp" OnSelectedIndexChanged="ListView_Comments_SelectedIndexChanged"><LayoutTemplate><table><tr runat="server" id="itemPlaceholder"></tr></table></LayoutTemplate><ItemTemplate><tr><td style="width: 460px; text-align: left; vertical-align:top;"><asp:Label ID="lbl_comments" runat="server" Text='<%# eval("comments") %>' CssClass="Form_Input_Font" Width="460" /><asp:HiddenField ID="Hidden_wo_comments_uniqueid" runat="server" Value='<%# Bind("wo_comments_uniqueid")%>' /></td><td style="width: 55px; vertical-align:top"><asp:Button ID="Button_Select" runat="server" Text="Select" CommandName="Select" 
                                                    Width="45px" Height="40px" CssClass="Button_ListView_Style" Style="background-image: url(~/images/nav/white_nc/check_sm.png);
                                                    background-repeat: no-repeat; background-position: center;"  /></td></tr><tr><td width="455px" align="left" colspan="2"><div style="height: 1px; background-color: #70DB93; width: 455px; float: inherit;
                                                    border: 0" /></td></tr></ItemTemplate><EmptyDataTemplate><asp:Label ID="lbl_EmptyPopUp" runat="server" Text="No comments information was returned"
                                            CssClass="Form_Input_Font" /></EmptyDataTemplate></asp:ListView></div></td></tr></table></asp:Panel></ContentTemplate></asp:UpdatePanel>

Here is the code-behind of ASCX-2

Public Class comments_popup
    Inherits System.Web.UI.UserControl

    Private _WO_Type_Uniqueid As Guid
    Public Property WO_Type_Uniqueid As Guid
        Get
            Return _WO_Type_Uniqueid
        End Get
        Set(ByVal value As Guid)

            _WO_Type_Uniqueid = value

        End Set
    End Property



    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
       
    End Sub

    Protected Sub SqlDataSource_comments_PopUp_Selecting(sender As Object, e As System.Web.UI.WebControls.SqlDataSourceSelectingEventArgs) Handles SqlDataSource_comments_PopUp.Selecting
        e.Command.Parameters("@WO_Type_Uniqueid").Value = _WO_Type_Uniqueid

        ListView_Comments.DataBind()
    End Sub

    Protected Sub ListView_Comments_SelectedIndexChanged(sender As Object, e As System.EventArgs) Handles ListView_Comments.SelectedIndexChanged

        Dim _txt_comments As TextBox
        _txt_comments = CType(Parent.FindControl("txt_comments"), TextBox)
        _txt_comments.Text = _txt_comments.Text & " Pop Up Test"

    End Sub


   
End Class

In the code-behind I am not actually grabbing the data just passing some test data for now. In the SelectedIndexChanged I put a break point and if I view the contents _text_comment.text its returning the data from the parent TextBox. However if I try to change the value as soon as the modalpopup closes the value doesn't change on the parent. I also tried tracing the parent and it seems the value does come back to the parent but for some reason resets back to the original value.

Any suggestions?