Show data over rolling months instead of calendar months in SSAS

I have a cube that shows order volume history, but showing the month to date numbers isn't that useful (since they're way out of whack with other full months). I want to include that data in some kind of display, but in a way that makes sense.

What's the best way to go about showing the last 30 days (or last month) over a previous period? If there's some way I can do that with my time dimension, great, but I figured I might need a calculation of some kind.

For example, since today is 7/12, I'd want to show the data for 6/13-7/12 as the most recent period, and then compare it to 5/13-6/12, and so on - that way, it would be e开发者_运维问答asy to see where the current month is trending, but with values that are inline size-wise with previous periods. Also, I'd figure that would make an easier KPI value, since I can compare movement from last month's values using the rolling one-month period for comparison.