page indexing of a gridview that is in a gridview

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VB

ASP.NET

Gridview

i have the below gridviews:

<asp:GridView runat="server" ID="GridView2" OnRowDataBound="gvChildGrid_RowDataBound"  Width="1000px"
        DataKeyNames="number"   AllowSorting="false" style="font-size:15px;"
        AutoGenerateColumns="False" BackColor="White" BorderColor="#E7E7FF" AllowPaging="true" HorizontalAlign="Center"
        CellPadding="4" GridLines="none">
        <%-- <PagerSettings Mode="NumericFirstLast" FirstPageText="first" PreviousPageText="previous" LastPageText="last" NextPageText="next" Position="bottom" PageButtonCount="2" />--%>
        <AlternatingRowStyle BackColor="#F7F7F7" />
        <Columns>
        <asp:TemplateField HeaderText = "Select">
        <ItemTemplate>
        <a href="JavaScript:divexpandcollapse('div<%# Eval("number") %>');">
        <img id="imgdiv" width = "20px" src="images/Alarm-Plus-icon.png" alt="" />
        </a>
        </ItemTemplate>
        <HeaderStyle Font-Bold="True"/>
        </asp:TemplateField>

        <asp:TemplateField HeaderText = "Number">
        <ItemTemplate>
        <%# Eval("number")%>
        </ItemTemplate>
        </asp:TemplateField>


        <asp:TemplateField HeaderText = "Name">
        <ItemTemplate>
        <%# Eval("name")%>
        </ItemTemplate>
        </asp:TemplateField>


        <asp:TemplateField>
        <ItemTemplate>
        <tr>
        <td colspan="100%">
        <div id="div<%# Eval("number") %>" style="display: none; position: relative;  overflow: auto">
        <asp:GridView ID="gvChildGrid"  runat="server" BackColor="Transparent" AutoGenerateColumns="false"
        style="Width:100% !important;"  GridLines="None"  Font-Names="times new roman" AllowPaging="True" CellPadding="4"  AllowSorting="True">
        <HeaderStyle BackColor="#8cc63e" Font-Bold="true" ForeColor="White" />
        <Columns>
        <asp:BoundField DataField="number"  HeaderText="Mobile Number" >
        <ItemStyle HorizontalAlign="Center" />
        </asp:BoundField>
        <asp:BoundField DataField="name"  HeaderText="Name" >
        <ItemStyle HorizontalAlign="Center"  />
        </asp:BoundField>
        </Columns>
        </asp:GridView>
        </div>
        </td>
        </tr>
        </ItemTemplate>
        </asp:TemplateField>


        </Columns>
        </asp:GridView>

i have a gridview gvChildGrid that is in a parent gridview GridView2

i need to code the page indexing of the child gridview gvChildGrid but i'm not being able to catch the event from the behind code... because from the code i'm not able to get the id of the gridview gvChildGrid

i need to write the below but i keep getting that gvChildGrid is not a declared

  Protected Sub gvChildGrid_PageIndexChanging(sender As Object, e As System.Web.UI.WebControls.GridViewPageEventArgs) Handles gvChildGrid.PageIndexChanging
    gvChildGrid.PageIndex = e.NewPageIndex
    gvChildGrid.DataSource = x.searchByName(TextBox1.Text)
    gvChildGrid.DataBind()
End Sub

so if i need to read the gridview i have to read it as below :

Dim gv As GridView = DirectCast(e.Row.FindControl("gvChildGrid"), GridView)
but in this case what should be the event? i need the event on the pageindexing of this gridview

any advices?