var checkOK = "0123456789";
  var checkStr = document.myform.tel_1.value;

  for (i = 0;  i < checkStr.length;  i++)
    {
    var checkKey = 0;
    ch = checkStr.charAt(i);
    for (j = 0;  j < checkOK.length;  j++)
            {
           if (ch == checkOK.charAt(j))
       {checkKey = checkKey + 1;}
        }
    if (checkKey == 0)
    {alert('not no。');return false;}
    }