Adding form fields on the fly

Hi all - I’m attempting to sum/add up values within 4 different form fields on the fly, but keep getting a result of NaN…not sure what I’m doing wrong…here’s my code:

function calculate(totalElement) {

    for (var i=1,app_pend_end=0;i<5;i++)
    app_pend_end += what.elements['textField' + i].value - 0;
    totalElement.app_pend_end.value = app_pend_end;

   if (totalElement)
   {   
      var calculation  = "";
      var overall = "";
      var fields = new Array();
      var userInputs = myform.elements;
      
      for (var f = 0; f < userInputs.length; f++)
      { 
          if (userInputs[f].className=='special_value')
          {
                  if (userInputs[f].value)
                  {
                      fields[f] = userInputs[f].value;
                  }
                  else
                  {
                      fields[f] = 0;
                  }
          }
      }
	  
      for (var i=0; i<fields.length; i++)
      { 
          calculation += fields[i];
          
          if (i!=fields.length-1)
          {
              calculation += '+';
          }
      }
      
	  document.writeln(calculation);
	  
      if (calculation!='')
      {
          overall = eval(calculation).toFixed(2);
      }
      
      if (overall!='')
      {
          totalElement.app_pend_end.value = overall;
      }

}
}

Hi all - think I found my answer…using different code that works in IE, although it doesn’t quite work in Friefox, which I believe is b/c of the onKeyPress event

function calculate()
{

AppPend = 0; AppRec = 0; AppAppr = 0; AppClosed = 0;
TotAmt = 0;

if (document.myform.app_pend.value > “”)
{ AppPend = document.myform.app_pend.value };
document.myform.app_pend.value = eval(AppPend);

if (document.myform.app_rec.value > “”)
{ AppRec = document.myform.app_rec.value };
document.myform.app_rec.value = eval(AppRec);

if (document.myform.app_appr.value > “”)
{ AppAppr = document.myform.app_appr.value };
document.myform.app_appr.value = eval(AppAppr);

if (document.myform.app_closed.value > “”)
{ AppClosed = document.myform.app_closed.value };
document.myform.app_closed.value = eval(AppClosed);

TotAmt =
eval(AppPend) +
eval(AppRec) -
eval(AppAppr) -
eval(AppClosed) ;

  document.myform.app_pend_end.value = eval(TotAmt);

}

just discovered I had an error in my form…works great now!

Forgot to mention, this code is within a PHP file…I’m adding up the values, then submitting the info into a database