getting error in nested grid view control

hi guys i am getting problem in nested grid view

<asp:GridView ID="GridViewCategory"
        CellSpacing="2" ForeColor="#42301c" Font-Bold="true" Width="940px" GridLines="None"
         AllowPaging="True"
         OnRowDataBound="InnerGridViewLessons_RowDataBound"
         DataKeyNames="QuestionSubjectID"
        AutoGenerateColumns="False" runat="server" BackColor="White"
         BackImageUrl="images/hdngbar_lc.jpg" CellPadding="4">
    <Columns>                                
        <asp:TemplateField HeaderText="Subject Name" >
            <ItemTemplate>
                <asp:Label runat="server" id="lblQuestionSubjectDesc" Font-Bold="True" Text=<%#Eval("QuestionSubjectDesc")%>></asp:Label>
               
                  <asp:GridView ID="InnerGridViewLessons" runat="server" CellPadding="4" Width="100%"                      
                       
                       BorderStyle="Solid" BorderWidth="1px" Font-Size="8pt"
                       BorderColor="#336699" GridLines="Horizontal">
                       <HeaderStyle BackColor="#336699" Font-Bold="True" ForeColor="White" />
                   </asp:GridView>
                             
            </ItemTemplate>
       <%-- <asp:BoundField DataField="QuestionSubjectDesc" HeaderText="Subject Name"  SortExpression="QuestionSubjectDesc" ShowHeader="False"  />--%>
        </asp:TemplateField>                            
         
    </Columns>
   
    <EmptyDataRowStyle CssClass="headingtitle" />
    <FooterStyle BackColor="#5D7B9D" Font-Bold="True" />
    <RowStyle BackColor="#F7F6F3" Font-Names="verdana" Font-Size="10pt" HorizontalAlign="Left"         />
    <EditRowStyle BackColor="#999999" />
    <SelectedRowStyle BackColor="#E2DED6" Font-Bold="True" />
    <PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />    
    <AlternatingRowStyle BackColor="#F7F6F3"  />
    </asp:GridView>

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

        Dim Query_questionSubjects = From t In dbINAP.PEN_QuestionSubjects _
                                     Where t.QuestionSubjectDesc <> "General" _
                                     Select _
                                      t.QuestionSubjectDesc, _
                                      t.QuestionSubjectID

        GridViewCategory.DataSource = Query_questionSubjects
        GridViewCategory.DataBind()
        GridViewCategory.HeaderRow.Visible = False



    End Sub

Protected Sub InnerGridViewLessons_RowDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewRowEventArgs) Handles GridViewCategory.RowDataBound

        Dim gv As New GridView()

        gv = e.Row.FindControl("InnerGridViewLessons")

        If e.Row.DataItem Is Nothing Then
            Return
        End If
       

        If e.Row.RowType = DataControlRowType.DataRow Then


            Dim tmpstr As String = Left(e.Row.DataItem("SubSysCode").ToString, 3)

            Dim dbSrc = From t In dbINAP.Pen_Answers _
                                 Select _
                                  t.Answer

            gv.DataSource = dbSrc
            gv.DataBind()
        End If


    End Sub


please help me out i am unable to solve it