Product based shipping, w/variables?

Been trying to find the right setup, and can't.

Scenario: multiple products, different prices, weights, etc. Each product has 3 shipping options - standard (ground), domestic overnight, and international.

Current coding allows some items to be added to cart without additional shipping costs (typically low value, low weight items).

By pricing every item with a baseline shipping charge, we can then alter the 'add-on' shipping if they select Item A, base shipping, quantity 1, then add item B which carries a $5 upcharge over the base, and it just adds the $5 to the shipping total.

Though ClearThinking has some product based shipping products, they indicate they don't have one that will accomplish what we are using now.

Here is an example of the shipping code we have been using:

Ship1 is ground, ship2 international, ship3 overnight domestic. This code resides with every item separately so we can define the 'add ons'...

Item 1

INPUT TYPE="hidden" NAME="ship1" VALUE="7.95"
INPUT TYPE="hidden" NAME="ship2" VALUE="39.95"
INPUT TYPE="hidden" NAME="ship3" VALUE="49.95"
INPUT TYPE="hidden" NAME="shipAdd1" VALUE="0"
INPUT TYPE="hidden" NAME="shipAdd2" VALUE="0"
INPUT TYPE="hidden" NAME="shipAdd3" VALUE="0"

Item 2

INPUT TYPE="hidden" NAME="ship1" VALUE="7.95"
INPUT TYPE="hidden" NAME="ship2" VALUE="17.95"
INPUT TYPE="hidden" NAME="ship3" VALUE="17.95"
INPUT TYPE="hidden" NAME="shipAdd1" VALUE="3"
INPUT TYPE="hidden" NAME="shipAdd2" VALUE="0"
INPUT TYPE="hidden" NAME="shipAdd3" VALUE="7"


In the above code, if you buy item 1, the standard shipping (ship1) is 7.95. If you then added item 2, it would add '3.00' to the total shipping since the base (ship1) is identical at 7.95, but shipAdd1 is 3.00. But if you bought item 1, then added a second of item 1, the total shipping would just remain 7.95 for the entire order.

If you buy item 2 first, the standard shipping would be 7.95 + 3.00 = 10.95. If you then added item 1, it would add '0' to the shipping since again, the base is the same 7.95 for all.

For every item we sell we have this code, and costs vary from item to item based on weight or value of each. I like this flexibility. Some of our products are heavier but of lower value. Some are lighter with higher value, therefore we have adjustments like this.

And in some cases, the 'add on' is the key - if someone buys one of our items that is 3 lbs and $200 value, it might carry a $12.95 shipping charge, but if they buy a second one, it will just add $5, and a third $5, etc. I need that sort of module and cannot find it.

Anxious to hear thoughts, suggestions, or leads on modules for this. Thanks.