Hi Aoife,

If the formula's column is immediately adjacent a column with data that
reaches down that far then double clicking when the cursor changes to
the finer filldown cursor will fill down the same number of rows as the
data in the adjacent column.

If the above condition doesn't apply then select the top cell with the
formula then go
Edit|Go to... type the address of the last cell for the formula into
the Reference box, then hold down the Shift key while you click
OK|Control + D|Control + Up Arrow to return to top of sheet.

Ken Johnson