function getReference()
{
  refno = document.npdForm.offRef.value.toUpperCase()
  month = document.npdForm.month.value
  errMsg = "The COTAX Reference Number you entered is missing or incorrect - please check and try again."
  var mod11 = 11 
  weighting  = new Array(13)
  weighting[0] = 6;	weighting[1] = 7;	weighting[2] = 8;	weighting[3] = 9
  weighting[4] = 10;	weighting[5] = 5;	weighting[6] = 4;	weighting[7] = 3;	weighting[8] = 2;	
  checkDigits = new Array(11)
  checkDigits[0] = 2;	checkDigits[1] = 1;	checkDigits[2] = 9;	checkDigits[3] = 8
  checkDigits[4] = 7;	checkDigits[5] = 6;	checkDigits[6] = 5;	checkDigits[7] = 4
  checkDigits[8] = 3;	checkDigits[9] = 2;	checkDigits[10] = 1
  var msgTxt = ""
// orig reg = /\d{10}A001\d{2}[A-Z]/
  reg = /\d{10}A001\d{2}[ACNPTWXYZ]/
  var refno = refno.toUpperCase()
  if (reg.test(refno) == false) {
    alert(errMsg)
    return false
  }
  else {
	var total = 0
	for (var i = 1; i < 10; i++) {
		var j = i - 1;		hold = "" + refno.substring(i, i + 1);		total = total + hold * weighting[j]
	}	
	var remainder = total%mod11
	if(checkDigits[remainder] == refno.substring(0,1)) {
		//alert("Cotax Reference is correct")
		error_count = 0
	}
	else {
		alert(errMsg)
    return false
	}
  }
  if (error_count == 0) {
    //alert("Your Reference number is correct." + refno)
    document.npdForm.offRef.value = refno  
 } 
  else {
	alert(errMsg)
  	return false
  }


}


function clearForm()

{
  document.npdForm.offRef.value     = ""               // clear value
  return
}