// JavaScript Document
function Calculator(QuantityID,Price,TotalID) {
	var quantity = document.getElementById(QuantityID).value;	
	var re = /^\d+(?=\.{0,1}\d+$|$)/;
	if (re.test(quantity)) {
		var total = 0;
		var price = Price;
		total = price * quantity;
		document.getElementById(TotalID).value = '$' + Float_Number(total,2);
	} else {
		alert('Invalid quantity, please try again.');
		document.getElementById(QuantityID).value = '0';
		document.getElementById(TotalID).value = '$' + Float_Number(Price,2);
		document.getElementById(QuantityID).focus();
		return false;
	}
	
}

function Float_Number(f,s) {  
	var re=/^[\d]+[\.]{0,1}[\d]*$/;  
  	if (!re.test(f)){return   false;}  
  	var t=Math.pow(10,s);  
  	var val=Math.round(f*t);  
	var dort=val-Math.floor(val/t)*t;  
	for (i=s;i>1;i--) {  
		if (dort<Math.pow(10,i-1)) {  
			dort='0'+dort;
		}  
	}  
	return ((s>0)?(Math.floor(val/t)+'.'+dort):(Math.floor(val/t)));    
}