Custom Shopping Cart

I have a client that wants a shopping cart with the ability to resize and reposition the cart contents- kind of like so they can build/view a "collection" or "gift set" before purchasing. I assume this must be done in flash but any idea where to start or what to tell them?

This can be done with jquery.

Are you sure its repositioning in a cart (purely aesthetical) or did they mean they want the ability to add/remove/change multiple products in the cart?

If first: http://stackoverflow.com/questions/427230/javascript-drag-and-drop-grid
If second: Almost every shopping cart supports this.