Try using a Pivot command instead of a Bars command.
We posted a short video on our YouTube channel to demonstrate:
Dynamically Sort Bar Graphs
Note that compared to the Bars command, which graph the data as listed in the data table. The Pivot command has more analysis features, can perform calculations, but also can sort according to the values.
In the video, here is the data:
If you plot each column using a Bars command, it will look like this.
Here is what the graph looks like using the Pivot command with following setting to sort the rows decreasing:
Hope that helps!