Graph: reverse data order?

I have a simple time-series graph with dates on the horizontal axis and another variable on the vertical. In the spreadsheet data columns I'm adding new data at the TOP of the columns, but I'd like the most recent data to appear at the RIGHT of the graph.

My data set shows, e.g., A5:A489 and B5:B489, and manually changing it to A489:A5 etc. doesn't work (has no effect, is automatically reversed... I forget exactly which).

How can I do this? Have new data, recently added at the TOP of my data columns, at the RIGHT edge of the graph... I couldn't find any "reverse" button buried in the options, as there was in the old Quattro Pro.

[725 byte] By [john.egger] at [2007-11-25 22:32:19]