[ic] Item based tax calculation in shipping.asc

[interchange-users@icdevgroup.org (Nora Heuer - Baytides Management Inc.)]

Hi all,
I currently have a working store (like a charm) that displays the Canadian PST (8%) on 
a separate line from the GST (using [salestax]) on the checkout page using the tag 
[shipping pst] and in shipping.asc I have:

pst	PST Ontario only	[subtotal noformat=1]	1	9999999	x 
.08		{'PriceDivide' => "1",}
pst	NO PST	[subtotal noformat=1]	0	0	0		{}

Works really well.

Now I'm working on a different store using a similar format, only the PST is item based, 
ie. PST only applies to items in a certain tax_category (lets call it "pst").

What I need is a formula for shipping.asc that calculates the pst only for items in the 
"pst" tax_category and adds them together, so that I can call it on the checkout page 
using the tag [shipping pst].

I'm not much of a coder, any input is welcome.

NoraBaytides Management Inc.
www.baytides.ca
1-877-265-0123