Auto-Select Data Source for Chart

I have a chart on sheet2 that pulls data from a table on sheet1 that is updated monthly.
(See example attachment. I cannot attach the real file)

In the real file, the data table is populated automatically at the end of each month. So, at the end of September, data will be in that column.
My problem is that I need to get the chart to expand its data source to include September columns as soon as the month is over.
i.e. Notice the chart only has July and August data... I want to use VBA to have the chart's data source include the September column data automatically on October 1st.

Thanks!