hi all.. i have a address.java file with a textField as PostCode. in that only number should accepted. if i try to enter characters in that it sould popup a message. these validation must be done in address.xml file only i tried by giving the validation as

           <testcase>  
                <messageType>error</messageType>
                <validationType>isDigit</validationType>      
                <validationRule>5</validationRule>     
            </testcase>

but its not working. plz anybody can help me in solving this