Date field countdown - show other fields when countdown is finished

Hi,

I have type where I have fields Date & Voucher. I would like to use Date field as countdown for Voucher field to become active.

For ex. I select value in date field for the future (let's say 7 days). When these 7 days counts down I would like to Voucher field become active and Date field would say something like "Offer active".

Possible or do I need some kind of custom template?