Order of subtotals /totals calculation

Hi, I ve tried to change the order of Coupons, Subtotal TAX and shipping total so that the calcultion will take place in a differnt order for my order total, but this does not seem to work.

I am using 1.3.7.

I offer free carriage over £40 but if customer uses a discount coupon and the order value goes under £40 they still are getting free carriage.

This is hurting my margin of a particular product set but I want to be able to offer this for all other orders. The reason for keeping the price low is it is a very competitive product and I need the headline rate. I m fine until someone uses a coupon/voucher.

So the aim was to get Zencart to re-calculate the subtotal with the coupon/voucher applied and then to calculate what carriage is for the order. i.e if the product is £42 and they have a 15% discount then the subtotal is: £35.70 so the order is less than £40 so shipping charge is added.

This does not seem to be effected by the totals order.

Is there a solution?

Thanks

Did you ever figure this out? I'm having the same issue.