Three buttons and one gridview

Here's the radiobuttonlist and Gridview code:
     <asp:RadioButtonList ID="Pending" runat="server" AutoPostBack="True" OnSelectedIndexChanged="Populategrid">
                     <asp:ListItem Value="F03">Over 300</asp:ListItem>
                     <asp:ListItem Value="350">Over 350</asp:ListItem>
                     <asp:ListItem Value="400">Over 400</asp:ListItem>
                 </asp:RadioButtonList>        <br />
        DDS Pending Cases over 250 Days 
                 based on File Date<br />
        </strong></span>          <%--
        <span class="style4"><span class="style1"><strong>Total Pending:</strong></span> </span>
      <asp:Label runat="server" id="CountLabel" Font-Bold="True" class="style2" CssClass="style1" />
--%> <br /> 
         <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" 
        DataSourceID="SqlDataSource7" EnableModelValidation="True" Width="331px" 
        CaptionAlign="Top" Height="126px" BackColor="White" BorderColor="#DCBE68" 
             BorderStyle="Solid" BorderWidth="1px" CellPadding="4" 
              HorizontalAlign="Center" CellSpacing="2" Font-Names="Arial" 
     AllowSorting="True">                           <Columns>
                               <asp:BoundField DataField="Doc" HeaderText="DDS" SortExpression="Doc" />
                               <asp:TemplateField HeaderText="Total Pending" SortExpression="cnt">
                                    <ItemTemplate>
                           <asp:HyperLink ID="HyperLink1" runat="server" 
                            NavigateUrl='<%# "PendingDDS.aspx?doc=" & Eval("doc") %>' 
                            Text='<%# Eval("cnt") %>'></asp:HyperLink>
                        </ItemTemplate>                                 
                                   <HeaderStyle Wrap="False" />
                               </asp:TemplateField>
                           </Columns>
                          <FooterStyle BackColor="#FFFFCC" ForeColor="#330099" />
        <HeaderStyle BackColor="#990000" Font-Bold="True" ForeColor="#FFFFCC" 
            VerticalAlign="Top" Font-Size="Medium" />
        <PagerStyle BackColor="#FFFFCC" ForeColor="#330099" HorizontalAlign="Center" />
        <RowStyle BackColor="White" BorderStyle="Double" ForeColor="#330099" 
                  HorizontalAlign="Center" />
        <SelectedRowStyle BackColor="#FFCC66" Font-Bold="True" ForeColor="#663399" />
    </asp:GridView>

Here's the code behind:

  Protected Sub PopulateGrid(ByVal sender As Object, ByVal e As EventArgs)
        'Select Case Pending.SelectedItem.Value        '   Case "300"
        Dim conn As New Data.SqlClient.SqlConnection(ConfigurationManager.ConnectionStrings("PendingClaimsConnectionString").ConnectionString)
        Dim cmd As New Data.SqlClient.SqlCommand
        Dim cmdPending As New Data.SqlClient.SqlCommand        With cmdPending
            .CommandType = Data.CommandType.StoredProcedure
            .CommandText = "GetDDS250"            .Connection = conn
            '.Parameters.AddWithValue("@doc", Request.QueryString("doc"))
            .Parameters.AddWithValue("@doc", Pending.SelectedValue)
            '            .Parameters.        End With
        Dim adapter As New Data.SqlClient.SqlDataAdapter(cmdPending)        Try
            conn.Open()            Dim ds As New Data.DataSet
            adapter.Fill(ds)            'GridView1.DataSource = ds
            GridView1.DataBind()        Finally            conn.Dispose()
        End Try