I did try that, but what it gives me is the total count of vessel activity in the cell, but not separated by unique vessels. For example, polygon "A" has 5 point records associated, and the statistics output was 5. however, when i look at my attribute table, only two vessels are associated: one vessel went twice, and the other went three times. So I cannot show this data. I need it to show the number of unique vessel IDs per polygon.