RSQ (Correlation)

Hi,

I have 6 known X's for which I would like to find the correlation coefficient with a single known Y. The problem is that the sample size (n) needs to be adjusted down whenever a X doesn't have data.

For example, in column F I don't begin to have data until row49 and so i only want to correlate row49 through the last row of data in column F (row375) with the same rows in column I.

How would I dynamically find all the values in a given column and then correlate those with the same rows in column I? The data will get larger and larger every month and so I need a formula to offset to the first non-blank row in a X column and then correlate with the same offset data range in column I.

Thanks,
John