Numeric textbox control from radiobuttonlist selection
<p>I've a radiobutton list like this;</p>

<pre><code>  &lt;asp:RadioButtonList ID="RadioButtonFirm" runat="server" RepeatDirection="Horizontal"&gt;
                            &lt;asp:ListItem id="option1" runat="server" Value="Firm Code" /&gt;
                            &lt;asp:ListItem id="option2" runat="server" Value="Firm Name" /&gt;
  &lt;/asp:RadioButtonList&gt;
</code></pre>

<p>and also an asp:button control</p>

<pre><code>&lt;asp:Button ID="btnSearchFirm" runat="server" OnClientClick="Validate();" Text="search" OnClick="btnSearchFirm_Click" /&gt;
</code></pre>

<p>and a textbox</p>

<pre><code> &lt;asp:TextBox ID="txtCriteria" Width="120px"  runat="server"&gt;&lt;/asp:TextBox&gt;
</code></pre>

<p>If I select Firm Code from radio button, user only select numeric value to txtCriteria textbox, else string can be entered. How to validate it?</p>
