InfoPath Dev

I am developing an Infopath which contains richtextbox. I have set some data validations rules on that. I want the user to be restricted to put the text beyond perticular character limit. I have tried to do it through conditional formatting but could not achieve. I even tried to achieve it through _OnAfterChange event of the richtextbox.   

       public void test_richtextabstract_OnAfterChange()

         {     

            string nodeText = e.newValue;
            if (!string.IsNullOrEmpty(nodeText) && nodeText.Length > 1000)
            {
                 string truncatedText = nodeText.Substring(0, 1000);
                 e.newValue =truncatedText ;
            }

}

Have you tried putting a validation rule on the field?  That seems to work.  Trying to truncate it is a bad idea because richtext is XHTML, which cannot be arbitrarily truncated.

I tried it but it does not restrict user to type the content beyond limit. BTW I think I am very near to the resolution.