Selected Answer
To the best of my knowledge there is no worksheet function which can access cell comments. Consider moving the values in the comments to a hidden column.
With 10K rows, moving the values should better be done using VBA. So, if VBA can access the comment, why not user a UDF (User Defined Function) to do the calculations without having a hidden column?
First off, yes, that could be done. However considering the effort required to maintain data in comments, further, considering the errors that must occur using such a complicated system for data entry and maintenance over 10K rows (!) I would very quickly forget about the idea. In Excel, data belong into cells.
Perhaps you can explain why some one thought using comments for such data a smart idea in the first place. Perhaps a link could be established between a hidden column and a comment. My drift is to use VBA to create a comment based upon an entry in a column which is then hidden. The user would see the comment but the system would use the value in the hidden column for calculations. That sounds very complicated, and it is. Perhaps, if you explain your reasons, a better way can be found.