Calendar "Compare Dates" Option Should be More Flexible

When looking at a single date range, using 7/11/2010 - 7/17/2010, I don't like that when I then select to "Compare Dates" and select the week prior (7/4/2010 - 7/10/2010), the "Change" column does the calculation based on OLD minus NEW (i.e. week ending 7/10/2010 minus week ending 7/17/2010 - see attachment).  The only way to get around this is to move the order of the date ranges to pull the old dates first; however, this doesn't seem like a great solution, since the report then shows the older data next to the prop/evar values.

It would be great if the "Change" column would calculate based on the left column of data minus the right column of data.