title: Validate two controls (CustomValidator)
body: <p>Before submitting the form I need to test if the sum ( txtA + txtB) is greater than 100. Is it possible to do this with a <code>CustomValidator</code>, because I don't know if I can choose the 2 textbox in controltovalidate</p>
  
  <pre><code>&lt;asp:TextBox ID="txtA" runat="server"&gt;&lt;/asp:TextBox&gt;
  &lt;asp:TextBox ID="txtB" runat="server"&gt;&lt;/asp:TextBox&gt;
  &lt;asp:CustomValidator ID="CustomValidator2" 
                       runat="server" 
                       ErrorMessage="CustomValidator" /&gt;
  
  &lt;asp:Button ID="Button1" runat="server" Text="Button" /&gt;
  </code></pre>
  
  <p>Thanks.</p>