function CheckCharacters(Allowed, Field, FieldName){

  var checkOK = Allowed;
  var checkStr = Field.value;
  var allValid = true;

  for (i = 0;  i < checkStr.length;  i++) {
    ch = checkStr.charAt(i);
    for (j = 0;  j < checkOK.length;  j++)
      if (ch == checkOK.charAt(j))
        break;
    if (j == checkOK.length)
    {
      allValid = false;
      break;
    }
  }
  if (!allValid)
  {
    alert("Please enter only valid characters in the "+FieldName+" field.");
    Field.focus();
    return false;
  }
  return true;
}

function CheckInvalid(Disallowed, Field, FieldName){
  var checkOK = Disallowed;
  var checkStr = Field.value;
  var allValid = true;

  for (i = 0;  i < checkStr.length;  i++)
  {
    ch = checkStr.charAt(i);
    for (j = 0;  j < checkOK.length;  j++)
      if (ch == checkOK.charAt(j))
      {
	    alert("Please enter only valid characters in the "+FieldName+" field. Cannot use " + ch + " character");
	    Field.focus();
	    return false;
	}
  }

  return true;
}