var isNN = (navigator.appName.indexOf("Netscape")!=-1);

function autoTab(input,len, e) {
	checkNumber(input);
	var keyCode = (isNN) ? e.which : e.keyCode; 
	var filter = (isNN) ? [0,8,9] : [0,8,9,16,17,18,37,38,39,40,46];
	if(input.value.length >= len && !containsElement(filter,keyCode)) {
	input.value = input.value.slice(0, len);
	var nextField=(getIndex(input)+1) % input.form.length;
	while(nextField <=input.form.length) {
		if(input.form[nextField].type=="text") {
		input.form[nextField].focus();
		input.form[nextField].select();
		
		return true;	
		}
		nextField++;
	}
	return true;
	}
}

	function containsElement(arr, ele) {
	var found = false, index = 0;
	while(!found && index < arr.length)
	if(arr[index] == ele)
	found = true;
	else
	index++;
	return found;
	}
	function getIndex(input) {
	var index = -1, i = 0, found = false;
	while (i < input.form.length && index == -1)
	if (input.form[i] == input)index = i;
	else i++;
	return index;
	}

// calculate the ASCII code of the given character
function CalcKeyCode(aChar) {
  var character = aChar.substring(0,1);
  var code = aChar.charCodeAt(0);
  return code;
}


function checkNumber(val) {
  var strPass = val.value;
  var strLength = strPass.length;
  var lchar = val.value.charAt((strLength) - 1);
  var cCode = CalcKeyCode(lchar);

  /* Check if the keyed in character is a number
     do you want alphabetic UPPERCASE only ?
     or lower case only just check their respective
     codes and replace the 48 and 57 */

  if (cCode < 48 || cCode > 57 ) {
    var myNumber = val.value.substring(0, (strLength) - 1);
    val.value = myNumber;
  }
  return false;
}