Is there a shortcut to make a cell negative?

I'm looking for a simpler way than "F2, home, -" for each cell or running a "=0-A1" in another column and then pasting the cells as values and deleting the column with the formula.

Grrrrrr! It seems there ought to be a simpler way to do it.

Control-D copies the cell above it... is there something like that for "make negative"? Oh, it'd be so great if you could select a range of cells and then do Control-whatever and it would make them all negative.