Is possible to create a report that has relative filter that is linked to a user filter?

For example:

Say I have a report that has the measure "Number of Orders" and "Order Date". I would like to create a report that shows the "Number of Orders" for the current week and previous week. In addition the report has a user filter that allows the user to select a week - set by default to current week.

If the user selects the current week (say 25 Jan 2013), then the report would look like:

                              "25 Jan 2013", "18 Jan 2013"

Number of Orders      125                  98

However, if the user selects the current week as "28 Dec 2012", then the report would look like:

Therefore the previous week value shown as "21 Dec 2012" is linked to the current week selected by the user using the user filter.

Is this possible? I know the the relative period filters work on the current date/time stamp.

Thanks

Sunil