Numbers: Make numbers negative

In Numbers, how can I convert a number to negative.

E.g.

200
233
186

Becomes

-200 
-233 
-186

In Excel, you can use tools like Paste Special, but these don't exist in Numbers.

Solution 1:

A workaround is to create a column with formulas like "=-1 * A1", then copy and "Paste Formula Results" (⇧⌘V). But I'm sure there are better solutions.

Solution 2:

It would be awkward, might not be worth the time, but you would need to program this in automator using numbers hooks for automation / accessibility. That way you could make a service to swap the sign of whatever is selected.

Short term, you'd manually change each or set up a function to calculate the negative of the selection and then paste the values over the source.

This is one of the features that just isn't baked into Numbers (yet).