Excel - PMT - NaN and Infinity messages

Excel - PMT - NaN and Infinity messages

Hello!

I use this snipet, to calculate PMT.
     
    
      
  1.  
    2. 
      
  2. function PMT(i, n, p) {
    3. 
      
  3.  return i * p * Math.pow((1 + i), n) / (1 - Math.pow((1 + i), n));
    4. 
      
  4.  }
    5. 
      
  5.  function CalculatePMTFromForm(idLoanAmount, idAnnualInterestRate, idMonths, idResult) {
    6. 
      
  6.  var i = jQuery('#' + idAnnualInterestRate).val() / 1200;
    7. 
      
  7.  var n = jQuery('#' + idMonths).val();
    8. 
      
  8.  var p = jQuery('#' + idLoanAmount).val();
    9. 
      
  9.  var pmt = PMT(i, n, -p);
    10. 
      
  10.   jQuery('#' + idResult).val(pmt.toFixed(2));
    11. 
      
  11.   }
    12. 
      
  12.   function performCalc() {
    13. 
      
  13.   CalculatePMTFromForm('LoanAmount', 'InterestRate', 'Months', 'Payment');
    14. 
      
  14.   }
    15. 
      
  15.    jQuery(document).ready(function() { performCalc(); jQuery('.calc').keyup(performCalc); });
    16. 
      
  16.   
    17. 
      
  17.  The result shown in this input box:
    18. 
      
  18.    <td><input id="Payment" size="11" type="text" value="" /></td>
    19.

If i delete the input box value or get negative value, or start the
value with 0, i get an error message in the result input box (NaN or
Infinity)

Could anyone help me to disable, or change this message text?

Thank you.