Enable Disable ASP.Net Validators in GridView Row based on CheckBox Selection

I have one gridview with two template fields check box and dropdown and my doubt is dropdown validation should occur only for check box selected items..

 In my form all the dropdown shows validation even though if check box is not selected

  <Columns>
                                        <asp:TemplateField>
                                                 <ItemTemplate>
                                                      <asp:CheckBox ID="myCheckBox2" runat="server" />
                                                 </ItemTemplate>
                                      </asp:TemplateField>

                                            <asp:TemplateField HeaderText="Type" 
                                                    ItemStyle-HorizontalAlign="Center">
                                                    <ItemTemplate>
                                                    <asp:DropDownList ID="ddltype" Width="100px" runat="server" 
                                                            DataSourceID="SqlDataSource1" DataTextField="Comp_Type" 
                                                            DataValueField="id"   AppendDataBoundItems="true">
                                                            <asp:ListItem Text="--Select Type--" Value="" />
                                                    </asp:DropDownList>

 <asp:RequiredFieldValidator ID="RequiredFieldValidator2" Visible ="True" runat="server" 
                   ControlToValidate="ddltype"  ForeColor="#FF3300" ErrorMessage="Please select">
                </asp:RequiredFieldValidator>
</ItemTemplate>
</asp:TemplateField>
</Columns>