limit number of character in ckeditor

HI

according below article i set limit characters for textbox

http://www.aspsnippets.com/Articles/TextBox-Minimum-and-Maximum-Character-Length-Validation-using-ASPNet-RegularExpression-Validators.aspx

now i want do it for CkEditor i wrote these code

   <CKEditor:CKEditorControl ID="CKEditorControl1" runat="server"></CKEditor:CKEditorControl>

         <asp:RegularExpressionValidator Display = "Dynamic" ControlToValidate = "CKEditorControl1" ID="RegularExpressionValidator3" ValidationExpression = "^[\s\S]{0,600}$" runat="server" ErrorMessage="please enter Maximum 600 Characters." CssClass="valid1"></asp:RegularExpressionValidator>

but it didn't work

what should i do?

Best Regards