function recompute_payment_quick_calc(objForm) {
	var principal = objForm.elements['principal'].value;
    var rate = objForm.elements['rate'].value;

    //no negatives
    if(principal.charAt(0) == '-'){
      alert('Please enter a valid number');
      objForm.elements['principal'].focus();
      return false;
    }
    if(rate.charAt(0) == '-'){
      alert('Please enter a valid number');
      objForm.elements['rate'].focus();
      return false;
    }

    //pre-process values
    var len = principal.length;
    var clean_principal = '';
    var clean_rate = '';
    var char_val = '';
    var found_period = 0;
    for(var i = 0; i < len; i++){
      char_val = principal.charAt(i);
      if(char_val == '.'){
        if(found_period == 0){
          found_period = 1;
        } else {
          alert('Please enter a valid number');
          objForm.elements['principal'].focus();
          return false;
        }
      }
      clean_principal += ((char_val != '$' && char_val != ',')?char_val:'');
    }
    len = rate.length;
    found_period = 0;
    for(var i = 0; i < len; i++){
      char_val = rate.charAt(i);
      if(char_val == '.'){
        if(found_period == 0){
          found_period = 1;
        } else {
          alert('Please enter a valid number');
          objForm.elements['principal'].focus();
          return false;
        }
      }
      clean_rate += ((char_val != '$' && char_val != ',')?char_val:'');
    }
    principal = clean_principal;
    rate = clean_rate;

    //validate digits
    if(!isFloat(principal) || !isDigit(principal.substr(0,1)) ){
      alert('Please enter a valid number');
      objForm.elements['principal'].focus();
      return false;
    }

    if(!isFloat(rate)){
      alert('Please enter a valid number');
      objForm.elements['rate'].focus();
      return false;
    }

    if(rate){
      var term = objForm.elements['term'].options[objForm.elements['term'].selectedIndex].value;
      // pay_per_year assumed to be 12
      var payment = compute_payment(principal, rate, term * 12, 12);

      objForm.elements['payment'].value = payment;
    } else {
      alert('Please enter a rate.');
      objForm.elements['rate'].focus();
    }
  }