It's time once to play Spot The WTF. You should know the rules by now; just see how many WTF you can find. I counted five. I'd rate the difficulty of today's exercise the same as that of finding the screaming man in Edvard Munch's Scream.

function bfIsAlphaNumeric( cfield )
{
  cfield.value = TRIM2(cfield.value);
  for ( i = 0 ; i < cfield.value.length ; i++)
  {
    var n = cfield.value.substr(i,1);
    if ( n != 'a' && n != 'b' && n != 'c' && n != 'd'
      && n != 'e' && n != 'f' && n != 'g' && n != 'h'
      && n != 'i' && n != 'j' && n != 'k' && n != 'l'
      && n != 'm' && n != 'n' && n != 'o' && n != 'p'
      && n != 'q' && n != 'r' && n != 's' && n != 't'
      && n != 'u' && n != 'v' && n != 'w' && n != 'x'
      && n != 'y' && n != 'z'
      && n != 'A' && n != 'B' && n != 'C' && n != 'D'
      && n != 'E' && n != 'F' && n != 'G' && n != 'H'
      && n != 'I' && n != 'J' && n != 'K' && n != 'L'
      && n != 'M' && n != 'N' && n != 'O' && n != 'P'
      && n != 'Q' && n != 'R' && n != 'S' && n != 'T'
      && n != 'U' && n != 'V' && n != 'W' && n != 'X'
      && n != 'Y' && n != 'Z'
      && n != '0' && n != '1' && n != '2' && n != '3'
      && n != '4' && n != '5' && n != '6' && n != '7'
      && n != '8' && n != '9'
      && n != '_' && n != '@' && n != '-' && n != '.' )
    {
      window.alert("Only Alphanumeric are allowed.\nPlease re-enter the value.");
      cfield.value = '';
      cfield.focus();
    }
    cfield.value =  cfield.value.toUpperCase();
  }
  return;
}

As an aside, if you felt left out yesterday because you didn't have a GUID of your own, then worry no more. Thanks to Andrew Stevenson (for finding the eBay auction), you can have a GUID custom made for you. You'd better hurry and bid ... quantities are very limited.