How to Apply a Formula to an Entire Column in Excel?

If I select a cell containing a formula, I know I can drag the little box in the right-hand corner downwards to apply the formula to more cells of the column. But if I need to do this for 300,000 rows, Is there a short-cut, similar to ctrl+space, that will apply a formula to the entire column, or to a selected part of the column?

Try double-clicking on the bottom right hand corner of the cell (ie on the box that you would otherwise drag).