I'm adding a formula to a column that I don't know in advance, and I need
to fill the formula down the same number of rows as there are in column A.

If I knew the column, I would do something like:

LastRow = Cells.SpecialCells(xlLastCell).Row
Range("F1:F" Trim(Str(LastRow))).FillDown

How can I do this?

Thanks,
Woody