Untitled

<html>
    <script language="JavaScript">
        function Data(evento, objeto){
            var keypress=(window.event)?event.keyCode:evento.which;
            campo = eval (objeto);
            if (campo.value == '00/00/0000')
            {
                campo.value=""
            }

            caracteres = '0123456789';
            separacao1 = '/';
            conjunto1 = 2;
            conjunto2 = 5;

            if ((caracteres.search(String.fromCharCode(keypress))!=-1) && campo.value.length < (10))
            {
                if (campo.value.length == conjunto1 )
                        campo.value = campo.value + separacao1;
                else if (campo.value.length == conjunto2)
                        campo.value = campo.value + separacao1;
                }
                else
                        event.returnValue = false;

            }


    </script>
</head>
<body>
    <form method=post action="">
        Data: <input type="text" name="txtdata" pattern="[0-9]" maxlength="10" size="10" onKeyPress="Data(event, this)">
    </form>
</body>