Hi Kathy,
People typically use NA() in a formula to prevent data points from being charted as a Zero.
There are many tutorials on the web like this one:
http://www.exceldashboardtemplates.com/how-to-hide-a-pie-chart-slice-or-stacked-column-chart-section/
So your formula might look something like this:
=if(b2>=90,90,na())
Steve=True
http://www.exceldashboardtemplates.com