Report Formula's effected by Query Prompt

Question

We are developing a report in WEBI where the user enters Jan - Feb 2010. 
One of the colums on the report need to do a calculation using the 4 prior periods.
Period              Plan          Actual         *** Error (4 Prior)
Jan 2010          100                98                1.8
Feb 2010          102               96                 1.7
In BEX we would indicate that the calculated key figure ignore the report selection criteria. 
Is there a way in WEBI to do the same?
The data needed for the *** Error is found in Sept 2009 - Dec 2009
We don't want to select that and have
Period          Plan    Actual    *** Error (4 Prior)
Sept 2090     100      98           1.8
Oct   2009     102      96           1.7
Nov  2009     100      98           1.8
Dec  2009     102      96           1.7
Jan 2010      100      98           1.8
Feb 2010     102      96           1.7
Thanks is advance

Answer 1

Hi...letme explain how works BO...since you enter Jan-Feb 2010 the data is coming from BI is restricted by query to Jan-Feb 2010 nothing more is coming if you want to see Sep-Dec 2010 you cant because the data was not be requested.
If you want to select the last 4 months always you could set separate month and year create a prompt for year, create another prompt for month and one more for las 4 months (this will be constant).
I believe this could work for you.
Regards