Variable products -> variable downloads

Is there a straightforward way to use variable products to configure a corresponding “Download” button when the product sold (or given away) is either Mac or Windows, various versions, etc.? Downloading is allowed, actually encouraged (in trial mode), before purchasing, so I want customers to be able to be able to select the variations on the product page, then have a Download button automatically point to the product they specified. Is that practical through either a plugin or with a hook of some sort that could be picked up by a PHP script? — Many thanks in advance for any suggestions!