Very mysterious to me that COLUMN() will not work in this case. I illustrate with an example to isolate the problem.
Fill in V1:V10 on Sheet2 dates 9/1/18, 9/2/18...9/10/18.
Enter into W1:W10 numbers: 15, 18, 9, 25, -15, 14, 7, 3, -7, 4.
There is a defined name "firstrow" which is = 1 (but...