UPS Next Day Air Rate

I built an e-commerce website - http://www.sadiessalsa.com

Everything is working well, except that we have one product Tamales http://www.sadiessalsa.com/sadies-pork-and-red-chile-tamales that needs to only ship Next Day.

We get real-time quotes from UPS (Ground - default, 2nd day, and Next Day) for all products, but on this one I'd like to make sure the **UPS Next Day** gets validated, so they can not proceed if they choose Ground or 2nd Day for the Tamales only.

Right now it defaults to Ground (which is desired for the other products), but people are ordering it with Ground. The messages in checkout aren't enough.

Any help will be greatly appreciated.

Thanks!