Is there any way to empty the shopping cart whenever a product is added outside of using the "e" option on the custom cart links?

I have three products, which are all mutually exclusive. Two of these products can only ever have a quantity of one (1). The third product can have a variable quantity (i.e. 1 or more).

When I only had the two original products, I was using custom cart links to include the "e" option to empty the cart. However, since adding the third variable product, I was hoping to use the add cart link default buttons using the display quantity option, which is really nice since it hides the display quantity field if the product enters a "0" default value.

Unfortunately, I haven't been able to find a configurable for emptying the cart on product add when using the add cart link buttons. I'm more then happy to do this within a module hook if I can find the right one as well.

Any advice is greatly appreciated. Thanks!