[Jc_Hoop]

Originally Posted by jmrker

What have you attempted thus far?

Basically its a fuel calculator. User selects fuel from a drop down list then enters the quantity they want into a textbox. This value is then selected as either litres or gallons using the radio buttons. Default value is litres radio button. If user selects gallons I want to multiply the litres value by 4.54.

User will also use a second set of radio buttons to choose which currency they want their fuel total to be displayed in.
I have this so far

window.onload = startForm;

function startForm() {
	document.forms[0].fuel.focus();
	
	document.forms[0].fuel.onchange = calcTotals;
	document.forms[0].litres.onblur = calcTotals;
	document.forms[0].unit.onclick = calcTotals;
	document.forms[0].currency.onclick = calcTotals;

function calcTotals() {

	// select fuel(price)
	var product = document.forms[0].fuel;
	var pIndex = product.selectedIndex;
	var productPrice = parseFloat(product.options[pIndex].value);
	
	// select quantity(litres)
	var quantityChosen = parseFloat(document.forms[0].litres.value);

	//var fuelUnit = document.forms[0].litre;
	
	finalPrice = productPrice * quantityChosen;
	
	// get subtotal(final price - tax)
	var subVal = finalPrice / 1.23;
	document.forms[0].sub.value = (subVal).toFixed(2);
	
	var taxRate = 0.23; //23%
	var taxVal =  finalPrice - subVal;
	document.forms[0].tax.value = (taxVal).toFixed(2);
	
	// get total price(subtotal + tax)
	document.forms[0].tot.value = finalPrice.toFixed(2);
}

Any help would be much appreciated and I thank you for your reply.