var
	principal,
	targetRate,
	realRate,
	buy,
	period,
	interestRate,
	reward=0;
	
function formatMoney(inVal){
	strIn = new String(inVal);
	if ( strIn.indexOf(".") == -1 ){
		dollar = strIn;
		cent = "";
	}else{
		dollar = strIn.substring(0,strIn.indexOf("."));
		cent = strIn.substring(strIn.indexOf("."),strIn.length);
	}
	count = dollar.length%3;
	if ( count == 0 ){
		count = 3;
	}
	result = dollar.substring(0,count);
	count += 3;
	while ( count <= dollar.length ){
		result += ",";
		result += dollar.substring(count-3,count);
		count += 3;
	}
	result += cent;
	return result;
}

function changePrincipal(){
	principal = parseInt(document.forms[1].principal.value);
	if ( isNaN(eval(principal)) ){
		document.forms[1].principal.focus();
		document.forms[1].principal.select();
		alert("Invalid input");
		return false;
	}else{
		document.forms[1].principal.value = principal;
		return true;
	}
}
function changeTargetRate(){
	targetRate = parseFloat(document.forms[1].targetRate.value);
	if ( isNaN(eval(targetRate)) ){
		document.forms[1].targetRate.focus();
		document.forms[1].targetRate.select();
		alert("Invalid input");
		return false;
	}else{
		document.forms[1].targetRate.value = targetRate;
		return true;
	}
}
function changeRealRate(){
	realRate = parseFloat(document.forms[1].realRate.value);
	if ( isNaN(eval(realRate)) ){
		document.forms[1].realRate.focus();
		document.forms[1].realRate.select();
		alert("Invalid input");
		return false;
	}else{
		document.forms[1].realRate.value = realRate;
		return true;
	}
}
function changeBuy(){
	buy = parseFloat(document.forms[1].buy.value);
	if ( isNaN(eval(buy)) ){
		document.forms[1].buy.focus();
		document.forms[1].buy.select();
		alert("Invalid input");
		return false;
	}else{
		document.forms[1].buy.value = buy;
		return true;
	}
}
//function changePeriod(){
//	period = parseInt(document.forms[1].period.value);
//	if ( isNaN(eval(period)) ){
//		document.forms[1].period.focus();
//		document.forms[1].period.select();
//		alert("Invalid input");
//		return false;
//	}else{
//		document.forms[1].period.value = period;
//		return true;
//	}
//}
function changeInterestRate(){
	interestRate = parseFloat(document.forms[1].interestRate.value);
	if ( isNaN(eval(interestRate)) ){
		document.forms[1].interestRate.focus();
		document.forms[1].interestRate.select();
		alert("Invalid input");
		return false;
	}else{
		document.forms[1].interestRate.value = interestRate;
		return true;
	}
}
function changeReward(){
	document.forms[1].reward.value = reward;
}
function calc(){
	if ( !changePrincipal() ){
		return;
	}
	if ( !changeTargetRate() ){
		return;
	}
	if ( !changeRealRate() ){
		return;
	}
	if ( !changeBuy() ){
		return;
	}
//	if ( !changePeriod() ){
//		return;
//	}
	period = document.forms[1].period.options[document.forms[1].period.selectedIndex].value;
	if ( !changeInterestRate() ){
		return;
	}
	
	reward = principal;
	if ( document.forms[1].iInvested[1].checked ){
		reward += principal*period*interestRate/36500/2;
	}
	if ( document.forms[1].updown[0].checked ){
		if ( realRate > targetRate ){
			reward += buy * (realRate - targetRate);
		}
	}else{
		if ( realRate < targetRate ){
			reward += buy * ( targetRate - realRate);
		}
	}
	document.forms[1].reward.value = formatMoney(Math.round(reward * 100) / 100);
}