http://authors.aspalliance.com/jotek...2/article.aspx

there is source code provided if you scroll down you will find....

here is the web site more detail.: http://authors.aspalliance.com/jotek...2/article.aspx

the part i'm confused or not sure how to use is the below, any help ?

<cc2:SelectiveValidator id=SelectiveValidator1 runat="server" ControlToValidate="RadioButtonList1" DisableValue="No phone" ValidatorToBeDisabled="RequiredFieldValidator1" Display="Dynamic" ErrorMessage="Select the phone type"></cc2:SelectiveValidator>