UPS shipping discout? is there such a plugin?

Hi.

We get our UPS prices at a discounted rate....is there a plugin that we can use to pass on this discount to our customers? A friend of mine said that there is a plugin that con be found in UPS website but I've no clue if there is as I couldn't find it (besides my friend is not using zencart so I'm not sure if that UPS application is made to work with zencart)....so that being said, has anyone made a module or plugin for shipping discounts, or different calculation of UPS based on some factors?

Thanks