Creator Reports: How can I sort the x-axis by y-axis value?

Creator Reports: How can I sort the x-axis by y-axis value?

I made a simple bar chart to show the total annual spending on travel for each employee. The y-axis is the dollar amount, the x-axis is the staff member.

My problem is that I can only sort the x-axis alphabetically. Instead, I would like to sort the employees according to their y-axis value - in other words, from the person who has the highest spending on travel to the person who has least. Am I missing the easy way to do this? I only see the button for sorting alphabetically...