bar chart - how to hardcode (-) x axis to (+) x axis?

[jim_chan]

Hi guys,

I am creating a comparion bar chart side  by side as below.  on the left (gross) bar chart,  how can I change the negative numbers to positive ? is just like a mirroring.

The expression is use for the Gross bar chart is sum(gross_sales) * -1

Rgds

Jim