## Calculate subtotals, totals and postage

Hi All,

Wondering if anyone can help me out with modifying the below script:

Code:
```<script language="JavaScript" type="text/javascript">
<!--

/* This script is Copyright (c) Paul McFedries and
Logophilia Limited (http://www.mcfedries.com/).
Permission is granted to use this script as long as
this Copyright notice remains in place.*/

function CalculateTotal(frm) {
var order_total = 0

// Run through all the form fields
for (var i=0; i < frm.elements.length; ++i) {

// Get the current field
form_field = frm.elements[i]

// Get the field's name
form_name = form_field.name

// Is it a "product" field?
if (form_name.substring(0,4) == "PROD") {

// If so, extract the price from the name
item_price = parseFloat(form_name.substring(form_name.lastIndexOf("_") + 1))

// Get the quantity
item_quantity = parseInt(form_field.value)

// Update the order total
if (item_quantity >= 0) {
order_total += item_quantity * item_price
}
}
}

// Display the total rounded to two decimal places
frm.TOTAL.value = round_decimals(order_total, 2)
}

function round_decimals(original_number, decimals) {
var result1 = original_number * Math.pow(10, decimals)
var result2 = Math.round(result1)
var result3 = result2 / Math.pow(10, decimals)
}

// Convert the number to a string
var value_string = rounded_value.toString()

// Locate the decimal point
var decimal_location = value_string.indexOf(".")

// Is there a decimal point?
if (decimal_location == -1) {

// If no, then all decimal places will be padded with 0s
decimal_part_length = 0

// If decimal_places is greater than zero, tack on a decimal point
value_string += decimal_places > 0 ? "." : ""
}
else {

// If yes, then only the extra decimal places will be padded with 0s
decimal_part_length = value_string.length - decimal_location - 1
}

// Calculate the number of decimal places that need to be padded with 0s
var pad_total = decimal_places - decimal_part_length

// Pad the string with 0s
for (var counter = 1; counter <= pad_total; counter++)
value_string += "0"
}
return value_string
}

//-->
</script>```
I got the script from this url:

http://www.mcfedries.com/JavaScript/OrderTotals.asp to see in action.

I need to modify it so that:
it will also calculate totals for individual product items as well as the total &

And also a postage value which is based on the total order quantities i.e. first item = \$7, then \$1 for each item after that.

Any help would be much appreciated.

Thank you.