Thanks for the great help so far. I did a small test, and it's working. But, for my real data, I think I need a little more help.

My data will come from several separate files, which I think I can just copy and paste to make them separate sheets in a workbook (right? - or can I work with them as separate files?). These will be huge - thousands of cells in each. Will I have to manually write the formula for each and every cell? Since each cell contains a reference to the cell number, this seems likely to be the case, but I'm hoping that there is a work-around. Also, I will eventually want to run this formula on differents sets of data that would be different sizes, so if there is any way to autogenerate this, I'd love to give it a try.

Thanks again for the formulas. I feel like I'm well on my way!


George