function numbersonly(myfield, e, dec){
	var key;
	var keychar;

	if (window.event){
		key = window.event.keyCode;
	}else if (e){
		key = e.which;
	}else{
		return true;
	}
	keychar = String.fromCharCode(key);

	// control keys
	if ((key==null) || (key==0) || (key==8) || (key==9) || (key==13) || (key==27)){
		return true;
	}// numbers
	else if ((("0123456789").indexOf(keychar) > -1)){
		return true;
	}// decimal point jump
	else if (dec && (keychar == ".")){
		myfield.form.elements[dec].focus();
		return false;
	}else{
		return false;
	}
}


// 
function totalAquCost(){
	pp = eval(document.yieldCalc.purchasePrice.value); 
	lf = eval(document.yieldCalc.legalFees.value);
	sf = eval(document.yieldCalc.surveyFees.value);
	dc = eval(document.yieldCalc.decor.value);
	sd = eval(document.yieldCalc.stampDuty.value = "0");
	
	//stamp duty calc
	if ((document.yieldCalc.purchasePrice.value > 60000) && (document.yieldCalc.purchasePrice.value <= 250000)){
		sd = eval((document.yieldCalc.purchasePrice.value*1)/100);}
	if ((document.yieldCalc.purchasePrice.value > 250000) && (document.yieldCalc.purchasePrice.value <= 500000)){
		sd = eval((document.yieldCalc.purchasePrice.value*3)/100);}
	if (document.yieldCalc.purchasePrice.value > 500000){
		sd = eval((document.yieldCalc.purchasePrice.value*4)/100);}
	//
	if (document.yieldCalc.purchasePrice.value == ""){
		pp = eval(document.yieldCalc.purchasePrice.value = "0");
	}
	if (document.yieldCalc.legalFees.value == ""){
		lf = eval(document.yieldCalc.legalFees.value = "0");
	}
	if (document.yieldCalc.surveyFees.value == ""){
		sf = eval(document.yieldCalc.surveyFees.value = "0");
	}
	if (document.yieldCalc.decor.value == ""){
		dc = eval(document.yieldCalc.decor.value = "0");
	}
	
	tacSum = eval(pp + sd + lf + sf + dc); 
	document.yieldCalc.stampDuty.value = sd;
	document.yieldCalc.totalAquisitionCost.value = tacSum;
	document.yieldCalc.purchasePriceB.value = pp;
}

//
function netAnnIncome(){
	
	wr = eval(document.yieldCalc.weeklyRent.value); 
	vp = eval(document.yieldCalc.voidPeriod.value);
	
	//
	if (document.yieldCalc.weeklyRent.value == ""){
		wr = eval(document.yieldCalc.weeklyRent.value = "0");
	}
	if (document.yieldCalc.voidPeriod.value == ""){
		vp = eval(document.yieldCalc.voidPeriod.value = "10");
	}
	
	yr = eval(wr * 52);
	
	naiSum = eval(yr - ((yr * vp)/100));
	document.yieldCalc.netAnIn.value = naiSum;
	document.yieldCalc.netAnInB.value = naiSum;
}

//
function grYield(){
	
	naiB = eval(document.yieldCalc.netAnInB.value); 
	ppB = eval(document.yieldCalc.purchasePriceB.value);
	
	//
	if (document.yieldCalc.netAnInB.value == ""){
		naiB = eval(document.yieldCalc.netAnInB.value = "0");
	}
	if (document.yieldCalc.purchasePriceB.value == ""){
		ppB = eval(document.yieldCalc.purchasePriceB.value = "0");
	}
	
	
	gySum = eval((naiB / ppB)*100);
	document.yieldCalc.grossYield.value = gySum;
}