Product accessories specific to different products

Just looking for a heads up on something really.

Basically I've inherited a site that has a cart (not eCart, which is the only cart I'm familiar with, but I think was back in V3), but they would like to change a few things.

At the moment the site sells furniture, and through the cart process, customers have the option to buy cushions. At the moment its set up so that all cushions are the same price.

You can see how it works by quickly going through the process (although obviously not to the point of buying anything!) here :

product.php?id=37

However, it turns out that different items of furniture come with different sized (and so differently priced) cushions.

I don't really want to go in and mess the whole thing up, as I'm not really that clued up on hand coding PHP at the best of times, let alone when it might mess up a shopping cart.

So my question really is whether or not this is possible using eCart, and how involved it is to set up?

Thanks.