Additional shipping cost for expedited shipment

Hi,

I have this shipping rules:

Standard Shipping and Handling Fee is:

To U.S. addresses: $8
To Mexico & Canada: $18
To Central & South America: $21
To Russia, Central and South East Asia $22

To Most other areas including Europe, Middle East, Japan, Korea, Australia & China $24

THERE IS NO ADDITIONAL CHARGE FOR A SECOND product IN THE SAME SHIPMENT.

AFTER THE SECOND PRODUCT THERE IS AN ADDITIONAL $4 CHARGE FOR EVERY TWO ADDITIONAL PRODUCTS IN THE SAME SHIPMENT.

FOR EXPEDITED SHIPPING WE OFFER DHL, EXPRESS MAIL OR INTERNATIONAL EXPRESS MAIL. AT CHECKOUT YOU CAN SPECIFY THE EXPEDITED SERVICE YOU DESIRE. SHIPPING AND HANDLING FOR EXPEDITED SERVICES IS THE ACTUAL COST OF THE SERVICE PLUS $4 FOR EACH 1 OR 2 PRODUCTS.

My problem is on the expedited shipping. Any help?

You could clone Item Rate item and set Zones to manage which one is used for what ...

Then you could customize it that when there are 2 items there is a charge for 1 ... but when greater than 2 it charges like normal ...

It would be a bit of customization but not a terribly hard process ...

NOTE: I am also assuming that:

Product A quantity 2 is the same as
Product A quantity 1 and Product B quantity 1

where both count as 2 or 1, based on what you have described ...

Thanks but I have really no problem with the zoning and item rate. my problem is how to add the shipping amount if the customer choose an expedited shipment. for instance, the customer Canada purchases 4 bags. Basing on the condition, the ORDINARY shipment will be $22 ($18 plus $4 for the next 2 products). If the customer is happy with the ORDINARY shipment, then he checksout.

But if the customer wants an EXPEDITED shipment, he shouold be able to have an option (perhaps a check box). In this case, the zen cart automatically charges $26 ($18 plus $4 for the next 2 products plus $4 for EXPEDITED shipment).

My probem is how to add this check box option for EXPEDITED.