Conditional clickbox in asp.net c# gridview
<p>I am new to Asp.net and C#, but I need to help my boss to design some web form.
Below is my code to design a big web form for user to input account and click on the checkbox. How can I make people click on the first check box, then the second checkbox will also be selected?</p>

<p>Please let me know what kind of question will help you understand what I want to accomplish. Thank you!</p>

<pre><code>&lt;%@ Page Language="C#" AutoEventWireup="true" CodeFile="default.aspx.cs" Inherits="Service_Solution" %&gt;
 &lt;asp:GridView ID="GridView1" runat="server"&gt;
    &lt;Columns&gt; 
        &lt;asp:TemplateField&gt;
            &lt;HeaderTemplate&gt;
                &lt;th colspan="30"&gt;Key Account Desk Service Solutions&lt;/th&gt;
                &lt;tr&gt;
                &lt;th style="width:0px"&gt;&lt;/th&gt;
                &lt;th&gt;&lt;/th&gt;
                &lt;th&gt;&lt;/th&gt;
                &lt;th colspan="4"&gt;Shipment Monitoring&lt;/th&gt;
                &lt;th colspan="2"&gt;Shipment Tracing&lt;/th&gt;

                &lt;/tr&gt;                   
           &lt;tr&gt;
                    &lt;th&gt;&lt;/th&gt;
                    &lt;th class="auto-style8"&gt;Customer Name/Location&lt;/th&gt;
                    &lt;th class="auto-style8"&gt;Account Number&lt;/th&gt;
                    &lt;th class="auto-style8"&gt;100% Real Time Proactive Monitoring  through QCC and QSMS&lt;/th&gt;
                    &lt;th class="auto-style8"&gt;100% Proactive Monitoring through NPTS&lt;/th&gt;


                &lt;/tr&gt;             
            &lt;/HeaderTemplate&gt;
        &lt;/asp:TemplateField&gt;

        &lt;asp:TemplateField&gt;
            &lt;ItemTemplate&gt;
                  &lt;asp:TextBox ID="txtName" runat="server"&gt;&lt;/asp:TextBox&gt;
            &lt;/ItemTemplate&gt;
        &lt;/asp:TemplateField&gt;
        &lt;asp:TemplateField&gt;
            &lt;ItemTemplate&gt;
                  &lt;asp:TextBox ID="txtNo" runat="server"&gt;&lt;/asp:TextBox&gt;
            &lt;/ItemTemplate&gt;
        &lt;/asp:TemplateField&gt;
        &lt;asp:TemplateField&gt;
            &lt;ItemTemplate&gt;
                  &lt;asp:CheckBox ID="CB1" runat="server"  /&gt;
            &lt;/ItemTemplate&gt;
        &lt;/asp:TemplateField&gt;
     &lt;asp:TemplateField&gt;
            &lt;ItemTemplate&gt;
                  &lt;asp:CheckBox ID="CB2" runat="server" /&gt;
            &lt;/ItemTemplate&gt;
        &lt;/asp:TemplateField&gt;    
    &lt;/Columns&gt;
&lt;/asp:GridView&gt;
</code></pre>