Woocommerce products : Check box for Variations ?

Hello !
I would like to know how to achieve this :
i have a downloadable product and would like to add variations, but that you could download with the main product !
exemple :

Mp3 Track is the main product

i have two check box to add Mp3 variation 1 and mp3 variation 2 !

how could i do that ? the variations just permit to choose between variation, not to add another downloadable product…

is the plug in product add on could help me for that ?

thanks for any help !

Dan

http://wordpress.org/extend/plugins/woocommerce/