private var phoneValidator:PhoneNumberValidator;

private function creationCompleteHandler():void
{
     //
     // Create validators
     //                
     // Phone validator

     phoneValidator = new PhoneNumberValidator();
     phoneValidator.source = phoneInput;
     phoneValidator.property = "text";

}


  <mx:Panel title="Phone number validator">        
        <mx:Form>
            <mx:FormItem label="Name:">
                <mx:TextInput 
                    id="nameInput"
                />
            </mx:FormItem>
            <mx:FormItem label="Phone: ">
                <mx:TextInput 
                    id="phoneInput"
                />
            </mx:FormItem>
            <mx:FormItem label="Email: ">
                <mx:TextInput 
                    id="emailInput"
                />
            </mx:FormItem>
        </mx:Form>
    </mx:Panel>

Use this as a sample script to code flex data validations

Flex Data Validator - Phone number validator

ActionScript 3