Dimensional report authoring

[Vick]

hello,
         I m doing a project on Dimensional Report Authoring, I need to display a chart for number of complaints by product category for last 4 completed quarters. My problem is how do I calculate last 4 completed quarters using the current date as reference. Current quarter should not be included.

Hierarchy for is:

Complaint Open Date->Opened Year -> Opened Quarter -> Opened Month -> Opened Day

The members of Opened Day are in format eg: 06-Apr-2006.

Any help is appreciated

Thanks,
Vick