Sigmaplot - two sided horizontal bar chart

#1
Hello!

I've recently downloaded Sigmaplot 13 in order to easily make graphs etc. for my master thesis. However, there's one thing i struggle to do.

I've captured butterflies in two forest types, and now I want to make a horizontal bar chart with the y-axis in the middle and the x-axis starting at 0 and ending at approx. 150 on each side - the two sides representing the two forest types.

Does anyone know how to do this?

Here's a picture of what i want to do!
http://imgur.com/gRQLCgo