An update was done today which many Excel users will find useful. You can now have a web query timeframe parameter which has two periods. A timeframe clause with two periods allows for period comparisons to be made directly in AQL. Previously such a timeframe clause had to be in the query parameter. Now you can have a timeframe parameter such as "thisMonth, lastMonth".

One nice thing this now allows is for a cell to contain a formula to build a month-over-month timeframe comparison for arbitrary months. I do this by entering the following formula in the timefame parameter cell:

=TEXT(DATE(YEAR(C3),MONTH(C3),DAY(C3)),"yyyy-mm-dd") & ":" & TEXT(DATE(YEAR(C3),MONTH(C3)+1,DAY(C3)-1),"yyyy-mm-dd") & "," & TEXT(DATE(YEAR(C3),MONTH(C3)-1,DAY(C3)),"yyyy-mm-dd") & ":" & TEXT(DATE(YEAR(C3),MONTH(C3),DAY(C3)-1),"yyyy-mm-dd")

In cell C3 I place a date such as "1/1/2013"
With that date present, the timeframe cell will have the value
"2013-01-01:2013-01-31,2012-12-01:2012-12-31"
which will compare Jan-2013 to Dec-2012. If I want to roll this comparison back a month, I merely change C3 to have 12/1/2012. All of my queries which reference this timeframe parameter cell will then refresh with a comparison of Dec-12 to Nov-12.