I need tax free attributes

We are trying to bundle a taxable product with a non-taxable service. Is there an easy way to do this as an "tax free" attribute?

We've also looked at doing some type of "If you pick this product, pick one of these sub-products".

I can't find a way to implement this easily.

Thanks,
Doug

I've actually set this up a little different without using attributes (using different products), but I still need to find a way to tax part of the product price and not the other.

If you need to see what I've done, check out the URL below....

http://store.freehandnetworks.com

Thanks,
Doug

I've made progress...

I've added another pricing field that will the be the basis of calculating tax.

Can someone point me to the file (or files) that I need to update next? I just need to change the field that the tax calculator looks at.

Thanks,
Doug