BIRT: setting the max Value of the scale in the y-axis dynamic

Hello everyone,
I'm working on a report where i have a Bar-chart. I'm trying to find a way to tell the y-axis to set it's max-scale value as the max value that it comes from the Data when placed on the Chart.

Please see the following picture for better understanding

I'm thinking of some like: calling the y-Data using : getOrthogonalValue() and determine the max value of it and then set this value as the max scale for the y-axis but i don't know how to implement it . So I would be thankful for your suggestions and help