Getting changed value from modalpopupextender

Hi,

I need to use modalpopupextender to confirm some value in my webform and perform some action.

User can change some value in textbox on modalpopupextemder and apply mod.

Problem is that when execute server side function, text box value in modalpopupextender was some before change.

There is a way to get changed value in control on modalpopupextender?

<tk:ModalPopupExtender ID="mp1" runat="server" PopupControlID="Panl1" TargetControlID="cmdInizioLavoro"
        CancelControlID="cmdAnnulla"  BackgroundCssClass="Background" DropShadow="True"  ></tk:ModalPopupExtender><asp:Panel ID="Panl1" runat="server" CssClass="Popup" align="center" style="display:none">            <div style="background-color: ButtonFace;border-color:black; border-style:outset;height:290px;width:400px" class="content-box-header">            <br />            <asp:Label runat="server" ID="Label85" Text="CONFERMA DATI" Font-Bold="true" ></asp:Label><br /><br /><asp:Label runat="server" ID="Label62" Text="Seriale" AssociatedControlID="txtSeriale" meta:resourcekey="Label8Resource1"></asp:Label><asp:TextBox runat="server" CssClass="text-input large-input" Autocomplete="Off"  ID="txtSeriale" ></asp:TextBox><br/><asp:Label runat="server" ID="Label86" Text="Modello" AssociatedControlID="txtModello" meta:resourcekey="Label2Resource1"></asp:Label><asp:TextBox runat="server" CssClass="text-input large-input" Autocomplete="Off"  ID="txtModel" ></asp:TextBox><br/><br/><asp:Label runat="server" ID="Label87" Text="Modello" AssociatedControlID="txtAccessories" meta:resourcekey="Label10Resource1"></asp:Label><asp:TextBox runat="server" CssClass="text-input large-input" Autocomplete="Off"  ID="txtAccessories" ></asp:TextBox><div style="float:right;padding-right:20px;padding-top:20px"><asp:Button ID="cmdAnnulla" runat="server" Text="Annulla"  CssClass="button" CausesValidation="false" /><asp:Button ID="cmdConferma" runat="server" Text="Conferma" CssClass="button" CausesValidation="false" OnClick="cmdConferma_Click"/></div>            </div></asp:Panel><asp:Button runat="server" ID="Button1" Text="Inizio lavoro" CausesValidation="False" style="float: right; margin: 5px" CssClass="button" meta:resourcekey="cmdInizioLavoroResource1" />

And my server side code

 Protected Sub cmdConferma_Click(sender As Object, e As EventArgs) Handles cmdConferma.Click

        Dim AccessoriMod As Boolean
        Dim SerialeMod As Boolean
        Dim ModelloMod As Boolean

        If txtAccessori.Text <> txtAccessories.Text Then
            AccessoriMod = True
        End If

        If txtModel.Text <> txtModello.Text Then
            ModelloMod = True
        End If

        If txtSeriale.Text = txtSerialNumber.Text Then
            SerialeMod = True
        End If

        If ModelloMod Or AccessoriMod Or SerialeMod Then
          ' execute update in DB
        End If

End  Sub