Well, assuming Gen VI brings the same system that the previous three generations brought, this is how you'd find out.
Hidden Power calculation only really matters if the IV number is either odd or even. It has nothing to do with characteristic.
I came up with one formula. If you make sure that:
Your HP IV is odd.
Your Attack IV is even.
Your Defense IV is even.
Your Speed IV is odd.
Your Sp. Atk IV is odd.
Your Sp. Def is odd.
Then your Hidden Power will be Ice.
The letters in the equation represent either 1 or 0, depending if it's odd or even, respectively. So, the equation is:
((1 + (2 x 0) + (4 x 0) + (8 x 1) + (16 x 1) + (32 x 1)) x 15 / 63
((1 + 0 + 0 + 8 + 16 + 32) x 15) / 63
Add those numbers together, that makes 55.
55 x 15 / 63
The result of this equation would be 13.0952381
Under all circumstances, this number would round down, making the answer to that equation 13.
Find the number 13 on this chart, and BOOM! Instead Ice-type Hidden Power. :3
The IVs I created, however, is just one of many. There are many other IV sets that can be used, this is just one of them. If you don't know your IVs, you can use the Manual Calculation on this page.
Hope I helped. :)