This one may be a doozy - attribute change in cart

OK, I am pretty familiar with Zen Cart and have made major customizations that work very well, thanks to the talented contributors that share their experience.

However, on this I am stumped.

Need to add the ability for a user to change the size attribute for a product directly from the cart.

I already have the drop down for sizes working, for example:

Product Name Size Price per Unit Total
A T-Shirt dropdown size $14.00 $14.00

Where the drop down box holds the sizes S, M, L

I already have it set up to submit the update form on select box change.

However, it doesn't work. It is using the update quantity form, so I am thinking I need to change something in the shopping cart class - my problem is, the way the session variables and arrays work with Zen work, I am having trouble getting the value of the attribute and price to change when I submit the form. I am hoping that someone with more intensive knowledge of the cart arrays can provide some assistance. Thank you so much!