Web Forms :: Displaying Custom Validator Error Message On Summary?

I have an aspx page with lots of controls on it. I am using a custom validator control (with the serverside validation). Is there a way to display the error message on the validation summary without writing Javasccript. I am a beginner in .NET and am not fluent in Javascript. This is the custom validator HTML

<asp:CustomValidator ID="CustomValidator1" runat="server" ErrorMessage="Invalid Date"
ControlToValidate="txtDate" OnServerValidate="ValidateDate_ServerValidate" ValidationGroup="vgSetUp"
></asp:CustomValidator>

This is the utility method am trying to validate for the entry on the UI, so that it takes dates only in these described formats If the user enters date in any other format, this method returns returns the Datetime.Mivalue(1/1/0001)

public DateTime GetFomattedDate(string dateString)
{
try
{
string[] formats = {
"MMddyyyy", // These are the accepted date formats for the UI
"MM/dd/yyyy",
"M/d/yyyy",
"yyyy/MM/dd",
"yyyy/M/d"
};
DateTime EffDate = DateTime.MinValue;
if ( DateTime.TryParseExact(dateString,formats, null, System.Globalization.DateTimeStyles.None, out EffDate))
{
return EffDate;
}
}
catch (Exception)
{
throw;
}
return DateTime.MinValue;
}
This is my customvalidator event handler(code behind)
protected void ValidateDate_ServerValidate(object source,servervalidate eventargs args)
{
args.IsValid = GetFomattedDate(args.Value) ==DateTime.MinValue? false:true;
}

I am able to validate it properly, but I cannot display the error message in the validation summary along with other messages. Anyone who is expert on Javascript can Help with the javascript function?