force uppercase in Marketpress coupon code box

I forced uppercase in the coupon code box with CSS - but I realized this actually made the problem worse because it doesn't actually make the font uppercase - just it's presentation - so customers THINK it's uppercase.

What do I hook into to force this with a hook?

We have custom code that when you make a new coupon in marketpress it syncs with stripe - but it syncs only a case-sensitive version and does not allow you to make a lowercase brother to the code... so I just need to force ALLCAPSALLTHETIMEEVERYWHERE