How do I sort a bar chart x order by y value?

How do I sort a bar chart x order by y value?

I have a table of invoices with customer name and invoice payment information.  I created a chart showing average payment time for each customer.  Currently, the x axis is sorted by customer name, but I want it to be sorted by the average payment time (so that customers who take a long time are on the left and customers who pay quickly are on the right).

The pivot table feature has sorting, which is nice, but I can't figure out how to do sorting in the chart.  Any help would be appreciated.