Volatility Calculation stopped working

I'm assuming that you have already opened your VB editor and stepped through the code using F8 and watched it take place in your sheet? If it used to work, and you're certain that your code has not been modified, then something in the sheet itself has been modified. If a cell moved, or a reference changed, then that could be what is cosign the problem. Your code/syntax looks to be in order.

Cross posting is generally frowned upon, so you shouldn't go to the Programming section and post, you should see about getting it moved there. Here is a link:
http://www.excelforum.com/excel-programming/

The code tags are in the formatting bar right above where you type your post. It's the button that looks like "#"