The small portion of it is the problem - that's where I'm getting stuck with error message. The rest of the script is working.

The reason I have to look back over the previous 15 rows is not relevant to the array problem. It's a requirement of the processing, nothing more.

The data value that I'm looking for changes because it's based on the several values in the current row of original data (which has 17 fields). Deriving that value is not an issue, the code produces the correct value to search for.