After trying to do this myself for a while I have finally realized I do not know enough PHP to continue.
I will be processing credit card transactions thru Paysystems.com tpp-pro solution. I have the documentation of requirements from them.
I need a cart that will allow me to click an item button that contains all of my product info: itemid, customerid etc. that opens a view cart page that can have additional items added to it and removed (continue shopping or remove item).
I would like from the same cart page to be able to select the shipping option (I have a module provided by USPS that I would like to integrate ) and have shipping and items calculated on that page to a grand total amount. Then on checkout send the information to Paysystems.
Basically what I want to do is what is done for most Pay Pal sites except I want to send the info to a different processor.
I do not need a database with this or any files for storage, the processing company has all that for order info and tracking.
If you would be interested in doing this for me I would like for you to get back to me at firstname.lastname@example.org and then from there we can discuss by phone Cost and any additional questions you may have. I do have a Pay Pal.