I used to be able to make negative values show without the minus sign in previous versions of PowerPoint (2003 and older), but 2010 no longer supports my custom number format. Does anyone know how I can still achieve this?

E.g., a vertical stacked-bar chart where segments with positive values (50%, 35%) go above the horizontal line and negative values (-15%) below it, but instead of showing "-15%," I'd like it to display "15%" in the negative segment, instead, and still stay below the line.

I'm pretty sure I should be able to format the number with custom formatting, but the syntax must have changed.

Much appreciated!