Upon checking chkEmailUpdates below:
<asp:CheckBox ID="chkSpecial" runat="server" Text="Email me updates" OnCheckedChanged="fncEnableEmailBox(Cheched)" />
the text box below (txtAddress, already disabled)
<asp:TextBox ID="txtAddress" runat="server" Enabled="False"></asp:TextBox>
is expected to fire fncEnableEmailBox() with an argument true or false to enable or disable txtAddress and also activate or deactivate its validation (unless validation is ignore when a control is disabled)?