Hi Gregg,
David is correct, the calculations run on the back-end. The only way to 'exclude' a story from the burn down would be if you had the Plan Estimate field set to '0'.
Yet, perhaps for curiosity more than anything else, why would you need to exclude/exempt a story from the burndown?
As long as this story is actually worked on then it should be estimated and burndown against the execution. Why should it not?
Thanks,
Sagi