asp CompareValidator error message publish check

See more:

C#

ASP.NET

errors

I have

<asp:CompareValidator ID="CheckToDate" runat="server" ControlToValidate="ToDateTextBox"
ControlToCompare="FromDateTextBox" SetFocusOnError="true" Display="Dynamic" Operator="GreaterThan"CssClass="ErrorLabel" ErrorMessage="<%$ Resources:GlobalResources, EndDateNotValid %>"Type="Date">
</asp:CompareValidator>

when my

ToDateTextBox

is smaller than my

FromDateTextBox

it shows the err "End Date Not Valid"
I want to be able to check is the error is published or not in my C# code
because I want to enable/disable a button based on it

Thanks