Link two attribute’s values with autoupdate whenever one is changed

I am looking for a solution to do this as i found nothing yet (and it’s been quite a few days).

So.. I need to sell wall decals and prints on my online shop that has WooCommerce installed. The wall decals and prints are measured by rectangular size and have a fixed ratio between height and width that varies on each decal (a proportional ratio for each product for so to speak).. but each decal can have a lot of widths and therefore lots of proportional heights and/or vice-versa. The thing is, whenever a client chooses a width or a height then the height or the width should be updated according to the specific proportional ratio of the product and automatically filled in. How can i do this?

Any ideas… or plugins that you might be aware of?